@mori_au @ReneeWestberry
Some instances are full-text searchable by default. I think some instances, you can opt in to full-text searchable for your posts. And I seem to remember that there's a link where, regardless of the policy at your instance, you can register and request that your posts be indexed for searchability? (Somewhere in my bookmarks; if that interests you, I'll go to a real computer and look for it.)

Regardless, #hashtags are searchable (I think).