If things get so bad on a board that a mod feels the need to post such a reminder, then things are bad enough for an Admin to be involved. It should not be the job of a mod to post messages reminding the posters of a board to play by the rules. Mods can't ban or restrict, so let the higher-ups take care of the offenders. Besides that, most posters know when their posts are being deleted, that should be a clue.
I don't have a problem with Mods posting a general reminder to abide by the rules as long as it isn't targeted to any individual (i.e. "you need to stop violating the rules or you're going to be banned").