Some of my posts and comments are not showing up on the original instance.

First example: Four days ago I posted an article to two different c/collapse communities. If I browse each community on their instance, my posts don't show up.
Example

Second example: I posted to a community but comments on my post don't appear unless I go to their instance. When I leave a comment it also doesn't show up for them.
Example

Can anyone explain what is going on?