I’m not really qualified to respond about creating great discussions because I pretty much just reply. But from the prospective of a participant, yeah I think it’s good to upvote any commenter that isn’t actively being a jerk. Even disagreeing comments can promote good conversation.

I wouldn’t suggest replying to every comment unless it contributes further to the conversation. That’s a judgment call, but posts where OP is replying to everything with “Thanks!” or “Yep” rub me the wrong way. Certainly reply to try to sustain conversation when there is more to discuss, and try to frame it in a way that invites not just the person you’re replying to but anyone to respond.

I think most topics are near death after about a day, but I browse by new and the only time I see more comments on posts I’ve already visited is if I get a reply or I’m looking through my comments later and open the topic to see what people said later. Topics that get more engagement live longer because a lot of people browse by hot.

Low effort to me is posting a link without summary or comment. The reality is unless the headline is a good summary or there is another comment or OP giving some context for why the link is interesting, I never click them, and then I have nothing to comment on either (usually).

Cross posting is fine. It’s slightly annoying when I’m a member of all five boards something is posted to but I’ve gotten accustomed, and sometimes the conversation can be different in different boards.

As far as Lemmiquette, I personally like people who stand by their words rather than deleting things that turn out to be unpopular. I don’t mind being the lone voice of an unpopular opinion. The threat of downvotes just makes me think harder about whether what I want to say is important to say right then and there and if I have time to back up any pushback. I don’t disagree as often as I want to, but I generally don’t delete comments unless it turns out I was really misreading something and responding to something in my own head rather than in the post/comment.

Make sure fediverse links are properly formatted so they go to the user’s instance cache instead of a direct url to the host server.

I am very quick to block folks I don’t think I can have a fruitful conversation with in good faith. I suspect as a poster, one would want to do less blocking than I do, but still I recommend doing it for peace of mind. Negative engagement or returning bad behavior just winds up making you look bad. A block prevents you from being tempted to respond to incendiary comments.

Oh and from personal experience, saying “I agree with 95% of this, but let me respond to this one thing where I disagree” is read as being an absolute refutation and can provoke defensiveness. Try to at least quote some of the stuff that you particularly agree with to take some of the bite out of any disagreement. Some day I’ll learn that better.

Good luck!