People on Mastodon are complaining about people talking about twitter, and posting their complaints to the hashtag #twitter which is very odd, as they could filter it.

I expect there will be filters on Lemmy eventually.

If it is software how do you know who has implemented it and whether the instance respects privacy?

I discovered google had recorded all the hashtags I had visited on mastodon. I thought I had turned off this recording, but there were additional categories which I think they have added since the last time I was there.

Of course the UK government and ISP record everything too, by URL, so that includes hashtags, even this post has a unique URL.