Short answers to GR (General Reference) questions should not be converted to comments. The best way to deal with a short answer to a GR question is the usual way: close the GR question, and ultimately delete the question if it does not improve.
An answer of mine was deleted and converted to a comment. The answer was a couple of words and a link to EtymOnline.com. Apparently the rationale was that the answer was “barely more than a link to an external site”. This is one of the reasons given in the FAQ for why an answer might be deleted. (FAQ#deletion)
The practical problem: deleting short answers to GR questions can leave answered questions on the unanswered queue.
The editorial problem: the sole test for whether to remove an answer is whether it “fundamentally answer[s] the question” (FAQ#deletion). If it does, it is always a mistake to close it. The reasons given in the FAQ are helpful, but should not be applied blindly. We explicitly acknowledge in the FAQ that some questions can “be definitively and permanently answered by a single link”: that is our definition of a GR question. (FAQ#close)
It is especially wrong to convert a valid answer to a comment. We discourage users from posting comments which answer a question; we tell them to “post an actual answer”. (privileges/comment) We should not make editorial choices which do exactly the opposite.