They are “disappearing” because of this sorting ability:
When sorting by votes, it’s hard to insert small action posts in between because they tend to be better understood in chronological order (aka “Activity”). The bug now is that there is a filter that removes small action posts for both sorting methods.
I will remove the filter when “Activity” is selected, which will allow the small action posts to appear.
It’s probably also useful to have a site setting that allows admins to set if the preferred sort order is by “Votes” or “Activity”, I think?