I only ever block spam. I don't block people with differing opinions to me because that's not how I roll. On the flipside, I block lemmy communities all the time - logic being that I'd rather sort by new and remove communities I have no interest in because you never know when something interesting you're not subscribed to can come up in your feed.
Easiest example being: I've never seriously watched Star Trek or considered installing Linux, but you bunch of cunts have convinced me into transitioning. I'm not quite at the stage of programmer socks, but I'm sure y'all will force my hand eventually... ❤