In my personal experience, one of the things I have a gripe with is that, in some cases, even when you get the "highest tier" MYO, some groups will limit you on how many high-tier traits you can give a character. I get the point that they're supposed to be recognizable, but... They're also meant to be the rarest thing? You usually spend QUITE a bit of money AND/OR time getting it in the first place. Having the species be recognizable as the species is one thing, sure, but limiting a person with a "higher tier" MYO to only being allowed to have 4 "higher tier" traits when that is the the ONE TIER that (usually) gives you actual freedom on the design... Not the greatest. You could simply just say "you aren't allowed to change (x) or (x)" and just let them do whatever else, not give them a strict "you can't use (x) amount of 'higher tier' trait!" But also maybe this one is just me being salty about the fact that rule was dropped literal months into the groups existence.
Kind of ties into the last one but another one is when certain traits that don't really cause issues are off limits for people? I remember I wanted to give one the of the characters I had the ability to speak because I had incorrectly assumed the species in question COULD speak (and I wrote and submitted a writing piece where this character spoke and it got approved, mind you) which was my bad, but I wanted to fix it by putting the trait on the character, since I had enough of the premium currency to tack on said ability as a "higher tier" trait. But... They didn't let me? And I didn't really get why? I don't remember what their explanation was. I guess it could be considered a big part of the species, breaking a "core aspect" of the species or something. But it's not like it's going to make the character unrecognizable from the species if I give them that ability.
I LOVE the concept of closed species, especially in smaller groups (maybe like ~50 people) because there usually isn't a more... Cut throat environment, for lack of a better term, in larger servers. Smaller communities are more lax, and there isn't as much user bias. Smaller communities are, as you can guess, more community-based, especially if they're also meant to be more "F2P" compared to larger communities where it's more of a "get a design from your favorite designer for (large price)!" or "get a really rare myo for (large price)!" kind of thing. Sure, those issues could still be a problem within those small groups, but if it's a smaller group of closer people then it's more possible to get the people in charge to listen and take feedback.
Also, just... The fact that if you want to leave a closed species then there's usually an entire new problem you end up with where, if you don't want to change the designs you have, you're kind of just stuck in the mud. The fact that it's kind of commonplace for groups not letting you just leave with the designs you made (understandable if they're someone else's, maybe like a moderators design or something) without you having to redesign them also leaves a bad taste in my mouth. Of course, I get it, you don't want something that isn't part of the species to not look like the species anymore, but some of them just... Don't really feel specific enough to warrant a redesign? Like my thought process is "would this character be recognizable as (x) species or just appear as a normal OC without any context of the species existing?" kind of thing.
Ooh text wall. I'm ok with pings btw! :3