In my case, the page keeps spinning but the post is not submitted, regardless of reloading the page or waiting for a long time.
There was one case where I cut down significantly on the amount of characters in the post and then it posted, but I have been unable to replicate this.
I have the same issue with image posts. If I submit them through the app the posts counter on my profile goes up, but there's no post. I also can't retrieve any posts for my own account. It says I have 3 but it shows none.
Comments work OK so I'm not sure what the problem is. I was worried I got restricted or something.
Edit: Comments seem to work as the OP suggests though. I get the spinner but they've been posted already.
Edit2: It seems like I can't post link threads either.
Edit3: Even worse, it seems like I can't see my own posts but others can. So I might have spammed Warhammer40k and tabletopminis and I can't even clean up my own mess.
Edit4: If I sign out and go to these communities I can see my own posts. I can also go directly to them if I have the link. I can also keep track of them by clicking the star button but it seems like my feed is broken.
Edit5: Oh my god I'm so fucking stupid. If you hide posts you've seen it'll also hide your own posts...