Thanks for running this, Tetra! I had a lot of fun with this, and from everything I've seen, other people did, too! On the whole I think this was a very successful RP. To answer your questions...
How did the pace of the campaign feel; With regards to the amount of events? Did it feel like a particular obstacle took too long or not long enough? Did you want more or less obstacles?
I think the pacing was good. With 2-3 weeks to work with, I don't think you could add many more twists/obstacles, and having fewer would probably feel slight.
Did you enjoy the events themselves, or did you find them confusing or dull?
I enjoyed the events! I did like the mankey scene more than the mantine scene, I think because that one felt a bit more "characterful" and open in how it could be approached. The crystals seemed a bit more prescriptive (hit them with an appropriate attack), and I think made it a bit harder for some people to participate, since they didn't have attacks of an appropriate type. Puzzles that require a high amount of coordination are tricky, I think, because it's easy for plans to get thrown off by one person not doing what's expected or for things to bog down because everyone's waiting on one/two specific people to post.
I think at some points the large group size was a detriment, as the puzzles (and most RP puzzles, tbh) can be solved by usually like four to six people, max, working together, so then you just have a bunch of people standing around not feeling like they have much to contribute. I think it would be worth experimenting with splitting the party or introducing more elements that give players clear and distinct roles to play in scenes, like you mentioned trying. Or, of course, player limits, though I don't know that anyone wants that. :P
I did appreciate that with e.g. the mantine island you laid out a variety of different avenues for solving the problem: people could build a raft, some people could fly, some people could free mantine, etc. In theory this should have allowed people to contribute in a variety of ways, but I think in practice it can be hard to get people to do that; one method is jumped on by the most active players, or seems like the coolest/most interesting, and people pile on it and then find their character doesn't necessarily have anything to do there. It's tough!
I do agree with Seren that it would have been nice to tie the individual puzzles in with the broader story more--like, we were never going to skip mankey island, since going straight from freeing mantine to the final boss battle would have felt pretty anticlimactic! (To me, at least.) But ultimately that ended up feeling just like a detour that was fun from an RP perspective but didn't really fit in with the larger story, i.e. we could have skipped it without any impact. Which is exactly what it was intended to be, I think! But I think having there be a more concrete benefit to having gone and done the thing (and maybe a more clear motivations for characters to pursue them IC) would make these sorts of sidequests feel more rewarding. In this case I think the prize was supposed to be the berries, but if those ended up changing the parameters of the boss fight at all, it was unclear. The mankey attack you planned but ended up cutting would also have been good.
Was any aspect of the campaign either too fast or slow (keeping in mind the intention of a 2-3 week campaign)?
Not really. Things slowed down midweek, which I think is just inevitable with people's schedules. Worth it to keep in mind; I don't think you can do much about it.
Did you find the concept of the ‘Resolve’ mechanic fun?
Yes! I think you did a nice job of running a boss battle that was much more about roleplay and interactions than attacks and numbers as such. If there was anything I would like to see here, it might be to see some more integration of traditional pokémon battling/attacks with the "resolve" or RP elements. As you mentioned, Keldeo was never knocked out in this fight, but it also wasn't clear to me throughout how he was doing in terms of health/on the fighty side of things--most big combos seemed to have more of an impact in terms of lowering resolve rather than because they did damage as such, and regular attacks didn't seem to do much of anything. This makes sense because you want to incentivize teamwork and creative thinking more than "my pokémon has flamethrower and that's super effective, I'm going to have it use flamethrower" on repeat, but I wonder if there's any way that the battle side of things could be fleshed out so people who maybe don't have as much to contribute on the RP side of things still have something they can do, even if they aren't able to coordinate a big multi-attack with other people. It might be helpful for new players or people in unusual time zones, etc.
Was the intended length suitable (2 weeks)?
I think the actual amount of time the campaign ran (about three weeks) feels more comfortable than two weeks. I think the only way you're going to cover substantial ground in two weeks is if you have a lot of people open to posting multiple times a day, which is probably unrealistic in most circumstances. So regarding your new question--yes, I would vote three weeks.
Did the general arc of the campaign and the proving of honor feel engaging?
I thought the campaign felt fun and engaging throughout, and I thought the focus on honor tied things together with Keldeo nicely and gave the campaign a nice thematic core that people could latch onto with their RP if they wanted--it could get a little deeper than a typical D&D one-shot, "get through the dungeon and these small skirmishes, defeat the boss, you're done." I think there's an opportunity to draw that out more through the whole of the RP that might enhance the fun a bit.
Most of the discussion of honor came up in the final boss battle; it was kind of there in the mankey fight, where nobody was battling in an honorable way, but it didn't seem to have much to do with the mantine island, and the theme didn't feel fully developed up until the final fight. It might have been fun to include some "tests of honor" earlier on in the story, so that the boss battle could feel like more of a culmination of what the previous scenes had introduced. Maybe some characters start out skeptical of the idea, for example, but come to appreciate the importance after what happens to them in the pre-boss scenes. Maybe the party's honor could be more severely tested before reaching Keldeo--this would give characters the opportunity to fail during one of the earlier trials, then have a more dramatic reversal during the boss fight. (Whereas most people are not going to take the boss fight as a time to have their character fail in such a way that it would potentially hurt the rest of the team.) In general, I think bringing the theme forward more in the early parts of the campaign would give people more opportunities to use it as an inspiration for their RP or craft a character arc with it, if they felt so inclined.
I did really enjoy that people ended up taking a variety of different approaches to understanding honor in the final fight without them being penalized, though!
Would you join future campaigns?
Definitely!
Were there any ooc or ic aspects that confused you or felt unclear?
Nope.
What were your favorite parts?
Mankey scene and boss fight, certainly.
Any questions about anything (even thought processes and such!)
I'm really curious where you'll take this next! Are you planning to just work through the Swords of Justice, or are you thinking you might bounce around to other legends first?
I'm tickled that you had originally thought to do honedge + mankey separately, but ended up combining them. I do support sword monkeys; can't be mad about that choice. The potential scene with phantom Kyurem also sounded like fun--drawing from Gates to Infinity Keldeo lore there?
I'm also curious what the final stage of the fight would have been... I was kind of prepared for the water all over the arena to come into play somehow (e.g. it gets poisoned and then everybody there has to deal with the poison's effects), but I guess as it was that was just to provide some justification for Keldeo jetting around real fast?
