The lack of “Lemmy etiquette” is basically the whole point of the project. There is no general rule. There are places for shitposting, there are places for serious discussion. The civility fetishists get their corner, the people who enjoy replying to bigots with pigpoopballs.jpg get their corner. There is a niche for everybody - and if there isn’t - you can start one without being completely isolated from the rest of the network (at least, initially).
The situation on Reddit was absurd. The “Reddiquette” rules were generally okay, but very open to subjective enforcement. I spent many years on Reddit. I browsed a lot of different communities on there. But if one person on a community I browse makes a post saying “look what this asshole is saying” on another community I browse, and I go there an make an insightful comment, I am now “brigading.” If somebody wants to politely debate whether trans people have a right to exist, or whether or not we should send the homeless to concentration camps, and I tell them to fuck themselves, I am being “uncivil.”
Communities need mods and admins who have their back, not mods who become cops for the admins who become cops for the board of directors who only care about increasing KPIs and profit. The coolest thing that can happen on the Fediverse is landing in a place where the admins will eat a block or two to defend the integrity of their communities. This is something which is simply impossible on Reddit.