This turned into a pretty lengthy answer. TL;DR: Flag as "not an answer", vote to delete, comment on the answer to let the poster know that it's likely to be deleted, and encourage them to participate elsewhere on the site until they have earned the necessary reputation.
There already exist several pro forma comments for this. Different people have slightly different variations on the theme; here are some of the ones that I use (these three by no means cover every possible situation, and some situations call for specific, custom-written comments):
Answers should be used only for actual answers to the question as asked, whereas it appears to me that this answer does not attempt to answer [OPusername]'s question. To ask for more information or suggest improvements, add a comment to the post in question. You can always comment on your own posts, and with a bit more rep, you will be able to comment anywhere. For the moment I've added the comment for you, and I'm flagging this post for deletion.
Answers should be reserved for actual answers to the question as asked. If you have another question, please ask it by clicking the Ask Question button.
Please don't add "thanks", "me too" and similar as answers. We're a Q&A community, not a conventional forum, so answer posts must answer (or attempt to answer) the question; answer posts which fail to do so are subject to deletion. Invest some time in the site and you will soon gain sufficient reputation to vote up posts that you like, which is the Stack Exchange way of saying thank you. Once you have sufficient reputation, you may offer a bounty to draw attention to the question.
In an ideal world, jokes would have no place on a Stack Exchange site. Consider the question comment box placeholder text:
Use comments to ask for more information or suggest improvements. Avoid answering questions in comments.
and for commenting on answers:
Use comments to ask for more information or suggest improvements. Avoid comments like "+1" or "thanks".
The aim here is obviously to indicate that comments should either ask for more information, or suggest improvements, relevant to the post the comment is attached to. Of course, all work and no play makes Jimmy a dull boy, but jokes come very far down the list of priorities here. The focus should be and remain to within each specific site's scope, asking quality questions and providing quality answers.
I personally think that occasionally, the relatively high reputation requirement for commenting prevents the very workflow comments are supposed to encourage, so I certainly see what you mean. Lowering the reputation limit for commenting is suggested every now and then, such as for example here, here, somewhat here, has been shot down here and commenting is in the MSE FAQ here. Just to point out a few questions on Meta Stack Exchange that deal with this very issue. The severity of this as a problem varies with how upvote-happy and active the community is; on our site, it's less of a problem than perhaps, say, on Physics SE.
The takeaway of all of those is basically that someone should show their ability to constructively contribute elsewhere, and then earning enough reputation to comment everywhere isn't very hard. And of course, once you have 200 reputation on any site in the network, you get to skip past all those pesky low-rep limitations on all sites thanks to the association bonus of 100 rep.
Within the framework that we do have, and assuming that the reputation limit is not significantly changed (note that even flagging is something you don't get to do at 1 rep), the best course of action for most people is to simply flag such answer posts as "not an answer", vote to delete if you have the necessary reputation, and clearly tell the user what they can expect. Leave a comment on their answer explaining that it is highly likely to be deleted, and encourage them to find other questions to which they are able to post solid answers that others can vote up. If the answer can be fixed with editing, encourage them to edit it. Teach them the ropes! I would also suggest to avoid downvoting unless the post is truly horrible; particularly to someone who doesn't know how our system works, a first experience being a downvote on something they wrote when genuinely trying to be helpful can be devastating.
We all started off at 1 rep at some point, with a brand new account on only one site, and clawed our way up from there. As frustrating as it can be for someone coming new to the site and seeing just the question they want to help figure out what the OP wants out of, unless the Powers That Be have a major change of heart we are pretty much stuck with these reputation limits for the time being.
Worldbuilding is a pretty upvote-happy community. It definitely shouldn't be hard to earn the 200 rep here needed for the association bonus to kick in, and the 50 rep to get to comment everywhere on the site should be easy. With our incredible diversity of subjects and question styles, I am willing to bet that we have a question for just about anyone where a newcomer can post a good answer, get some upvotes, and get started on the site.
And if all else fails, just point them toward our very own unicorn question.
