@julian No, no, no!! Hashtags are for IRC channels! Always have been. On the 'net, anyways.... ;-P
I have thought about the tagging thing on and off a few times over the course of using NodeBB. At first I missed the absence of tagging individual posts. Figuring that the NodeBB crew were smarter than the average bears, I figured they must have some reason or another figured for omitting such. Alas, the only thing I could figure was "tag pollution". Kind of like too many chefs spoil the broth kind of deal, too many tags, and perhaps ensuing gamification thereof by those desperate for attention/upvotes could result in them becoming essentially useless. Herding cats, entropy always increases, etc. Substitute whatever analogy floats yer' boats.
Forums excel at promoting long running, in depth conversations. Too many distractions are deriguer for the "ADD Generation". Hence, while I can see how hashtags would be an asset for something like Twitter, I wonder about posts wh/actually contain some meat, rather than just a bunch of "me too's" pointing to various other "me too's". Hmm...
So we should ask ourselves; "What purpose do tags actually serve? What itch do they scratch?". I think not many, actually, other than one: A quick substitute for lame and/or non existent search functionality. Maybe another side benefit for the lazy would be that tags are amenable to "clickery" driven UI's. This revelation then begs the question of how many new things we might invent to solve "problems" supposedly already solved by other previously invented "solutions". And maybe, just maybe, rather than proliferating yet another new thang... we should focus on improving the original thang that was supposed to solve these issues: Search that works? And what would that look like?
Hmm... just a bit of thought food here for inquiring minds.... 🤔
P.S.; Not meaning to disparage anyone's efforts here but rather stimulate further discussion.