We’re still working to find a solution for the posting slowness in large communities.
We have seen that a post does get submitted right away, but yet the page keeps ‘spinning’
So right after you clicked ‘Post’ or ‘Reply’ you can refresh the page and the post should be there.
(But maybe to be sure you could copy the contents of your post first, so you can paste again if anything would go wrong…)
Reading more about how this works, sending out updates to each instance shouldn’t block the request from returning unless you have a config flag set to debug source.
It might be due to poorly optimized database queries. Check out this issue for more info. Sounds like there are problems with updating the rank of posts and probably comments too