If you're wondering why I've started using hashtags on here in spite of them not working too great over federation, it's for two reasons:
1. It's an easy way for me to organize my own toots. Hashtags work just fine when not crossing instance boundaries, and I can find all of my education news toots with a single click now.
2. My crossposter used to post all of my public toots onto my nearly abandoned Twitter account, but today I narrowed it down to a handful of hashtags.
This may change.