If you go to the inbox and tap a comment, you’re supposed to go to that comment, right. Most apps do that just fine even if it’s a long thread, but mlem just kinda throws you in there somewhere and you’re left to figure out where that one new comment actaully is.
Once you’ve read that comment, you go back to the inbox and that old message is supposed to go away while the unread ones will remain. With most apps this works reasonably well, but with Mlem it’s a bit random.
If you find an interesting post with a picture, you might want to zoom into it. With all the other apps you can do that, but Mlem doesn’t have zooming yet.
What if you wrote a hasty comment and you realize there’s a typo or a factual mistake. With all the other apps you can just edit that comment, but Mlem doesn’t have the editing feature.
Have you ever wondered how many downvotes a comment or a post has received? With some apps you can actually see that, but Mlem isn’t one of them.
Usually on Lemmy you’ll find links to interesting articles, but once you click them you might want to use a very specific browser such as Firefox Focus or something. With most Lemmy apps you don’t even have that option, and Mlem is in that crowd.

Other than those points, Melem is a solid Lemmy app, and I’ll be keeping an eye on its development.