The Lemmy devs have already decided that karma is just a bottomless pit that just harms users mental health, so it’s highly doubtful we’d ever have a reputation system be introduced, as that’s literally the same thing.

Also, captchas can be preventative to people with certain disabilities, so introducing them (I believe it would be reintroducing, actually) would contradict Lemmy’s disability-inclusive culture. As well, email verification wouldn’t work for people who would prefer anonymity. And nefarious users could just use a spoof mail account, so the introduction of required email account verification would really only harm privacy-focused real users, and do nothing to prevent trolls. Also, while on the subject and though you didn’t mention it, we don’t ban IPs because some VPNs reuse them for multiple people. So banning the IP of a troll might also cause the ban of real users.