By calling posts "joke answers", you're actually giving those people power by acknowledging them. Just delete comment and move on. I think people trust you mods enough that if you delete a comment, you had a good reason to do so.
We believe, and the sentiment is generally supported by the periodic polls we do of the users, that a certain level of public moderation is important to maintaining the standard we expect in the subreddit. When we post a distinguished comment of that sort it is serving two purposes:
First it is a reminder to everyone of the rules.
And second it is a warning to that specific user to cease their behavior, or face the consequences.
We try to be judicious in when to hand out the warnings to keep from flooding the subreddit with them, and I would estimate that only 1 in 10 removed comments at most ends up with a distinguished comment.
The vast majority of removed comments are removed silently. This minimizes clutter in the thread, and doesn't make a big deal out of minor infractions. A downside, however, is that Reddit does not notify users that their comment was removed, and (assuming the user is logged on with that account) the user can still see their comment as if nothing has happened. So the user is none the wiser that a rule has been broken.
A few thoughts on moderator removal responses:
Our readers often ask for more explanation of removed comments, so we try to strike a balance between being unobtrusive vs. having transparency
as Zhukov says, we use these opportunities to educate the user and everyone else reading the thread: new people need to learn the rules, and everyone could use a refresher now and then
Users are often upset if the mods come down hard for a seeming 'first offence': warnings provide a referenceable dialog, and help the mods identify repeat offenders & guage how to respond (ignore, reminder, formal warning, temp ban, ban...)