I think this is partially correct. People write for themselves, but they also write for an audience. The latter is a problem because they can essentially ignore whatever they are responding to as long as triggers n upvote. This disincentivizes honest and productive dialog in favor of nitpicking, gotchas, or simple ridicule.

The former is like a bunch of drunk grandpas mumbling to themselves in a room, the latter is like a self interested orator playing to a crowd. Asynchronous written debate can be the one of the best forms of communication. Think about Jefferson’s letters or other famous correspondence. The incentives are just wrong on boards with ranking and voting