old.lemmy does this thing where you can't see any replies under you if someone you blocked replied as well

Do you mean it doesn't show replies from blocked users (which would be correct), or that you can't see replies to your comment if there's a sibling comment from a blocked user? I'm slightly confused 😅

But in general, if you find any odd behaviour or bugs in mlmym or if you have feature requests, feel free to send them to #mlmym:mschae23.de, !mlmym@lemmy.world, or mlmym@lists.mschae23.de, whichever you prefer :)