Take a look at this answer.
I took time to leave a comment to indicate to the answerer what he should do. It seems unfair to just skip it in the end.
What is the correct course of action ?
First off, you should always seriously consider skipping, especially if you know nothing about the property in question. Skipping isn't the mark of failure, it's simply a way of saying that you genuinely think that someone else might be able to objectively assess the answer better than you can.
So what are your remaining options?
Looks OK - Not appropriate. Even a cursory glance shows that the answer doesn't address the key point raised (e.g. what would happen?) and while it's perfectly acceptable to disagree with the main thesis of a question, you need to explain (in pretty solid detail) why the question's assumptions are wrong.
Edit the Answer - Not appropriate. You don't know anything about Halo and anything you add (beyond fixing grammar and spelling) would be sheer guesswork.
Mark for Deletion - This is the correct option. In its current state, the answer simply doesn't address the question. Once it's deleted, It's not gone forever and the OP can still improve it further and vote for it to be reopened. If you're genuinely in agony, you can always leave a comment.
As it happens, one of your friendly mods has already converted the question into a comment, where it belongs.
