take as an example this post: http://www.incatena.org/viewtopic.php?p=944466#p944466

under the primitive and un-2014 system of phpbb, i either have to remember which page in the thread that is on in order to find it [thus necessitating that i know of its existence] or approximate hashtags by putting a size=1 string like "aslian nonconcatenative morphology infix infixes infixation reduplication incopyfixation" at the bottom of the post, which 1) is Effort 2) is an ugly hack — and from these two points we may surmise that it will be uncommon, and therefore pointless to do.

however, if there is a system in place that directly encourages tagging, it will presumably be used for search, and therefore it will be worthwhile to tag posts. if i want to find everything on the zbb about nonconcatenative morphology, i have to have the entire board memorized; if i want to find everything on atlas-plus-hashtags about nonconcatenative morphology, i just hit the #nonconcatenative_morphology hashtag.