You are not mistaken, there are many things currently missing.
The 'community' system on steem is relatively new, and was made just before some mass-exodus table-flipping drama, so the activity log wasn't finished, and 'thread bumping' isn't displayed.
These things have potential to be resolved over time,
but for now it is a little less functional than a normal forum in certain ways.
Side effect of how these forums work, and how "Trending" is always default, sometimes the voting legion is slumbering and thus some new posts just don't even show up in Trending because every other post has like 40 votes and the new ones have 2.
-main_gi