I like the suggestion of hashtags — simple, and pretty universal meaning.
May be slightly confusing that in the composer # works as convention for referencing both tags and categories. One thing that might mitigate that would be keeping the # shortcut to search/select both categories and tags in the composer, but styling categories differently in the preview and post…
But yeah I think seeing the # in search results makes it a bit clear those are tags w/o having to label them. Also for short ones on the same line, makes it somewhat more clear they’re separate entities vs. e.g. a single two word phrase.
One other tiny thing, looks like the font size in search results is currently slightly larger for tags vs. categories? Categories feel like they should be bigger/more important, generally, idk if that balance could be tweaked a bit. In general this looks great though.