I find that, when possible, prevention is better than reactive measures. Our Discourse forum has community guides, and we PM users with tips/suggestions/etc. Once we PM someone, we rarely have issues with them repeating that mistake, so our education is 
. Despite that, we constantly have to deal with the same issues because new users are added to the forum and make the mistake for the first time.
This is not pleasant on moderation or anyone reading the forum. You could argue that we could improve our “welcome to the forums”, but if we added every nitpick to that, it’d become a gargantuan word wall that nobody would want to read. A much better solution for things like these is to prevent them in the first place – it’s not feasible to communicate all of them to new users, and it only worsens their first impressions of the forum.