I've recently started working through AI safety posts written on LessWrong 1-3 years ago; in doing so I occasionally have questions/comments about the material. Is it considered good practice/in line with LW norms to write these as comments on the original, old posts? One hand I can see why "necro-ing" old posts would be frowned on, but I'm not sure where else to bring it up. You can look at my comment history for examples of what I mean (before I realized it might not be a good idea)
Nope. That's part of the value in commenting/voting on old posts. You're mostly going to care enough to do so on the ones that seem relevant to you, which are the ones that might be worthwhile for others to look at.