Babelproofreader repeatedly tried to post the fact that his question was answered on dsp.SE as an answer so it could be accepted and receive the bounty, but his answer was converted to a comment each time.
There is an automatic system which, if an answer is exceedingly short and it contains a link to a question on the network, then it is automatically converted into a comment. This is mainly to catch people who post duplicate links as answers (and nothing but the link), rather than as comments.
However small the answer could be, it's generally better to do something more than just "The answer is here". Whether it is on the network, or found on some external site, it is always better to include relevant information from the link on the actual answer body.
So in this scenario, rather than continually posting the same tiny link answer that won't fall through, the answer should contain the essentials from the Signals answer. That way, it gives an actual complete answer on this site. The link to credit the original answer should be retained, of course, as long as the whole answer isn't just the link. One might consider using a community wiki answer, as you're basically answering on behalf of another user.