A dedicated federated service was my first idea - I've been meaning to play around with Fedify for that reason. On the other hand it's not really my area of expertise, and I didn't want to be that guy who drops in to be like "can somebody build this software I want?" Lol.
Would totally try to contribute though.
Gotcha - I never really got into the microblogging format (Fediverse or not), but now that you mention it I have seen a couple of posts like you describe.
Browser extension wouldn't be my first (or tenth) actual choice, I'm basically spitballing for what the easiest way to get some basic filtering would be (activity, band, area, mode, QRT status etc.). You might be onto something with Mastodon bots - I remember a HRWB episode where they talked about using that mechanism for finding radio related content I think - a bot that automatically boosted posts meeting certain criteria (only vaguely recall).
No real benefits, unless you count living in a particular place where there aren't really other options as a benefit. We moved to one because it seemed low key and we wanted to live in the country. The only other options were $$$$$$ on large acreages.
It didn't stay low key, and I had to become president to stop the busybodies - I'd push to get rid of the HOA entirely if it were possible, but we own shared infrastructure and have to manage it (roads, water, sewer).
Should our neighborhood have been allowed to develop in that way? Probably not, but we're stuck with it.
Thinking some more, Mastodon seems to support a pretty robust API:
https://docs.joinmastodon.org/api/guidelines/
Maybe it would be feasible to start putting together a set of standard hashtags to write a simple viewer/spotter against with the API?
#POTA #SOTA #WWFF #SSB #CW #FT8 #OTHERMODE #20M #10M #PARK_US_2299
etc.
Kinda clunky, but it would be easier than spinning up a full new federated app, and wouldn't have the side effect of potentially fracturing the community...