Why are we commenting rather than editing questions?

Question

I recently added an answer to a question about chains falling off a single chainring on the front when there is no derailleur. The answer is here.

There has been lots of interesting content added in the comments to the answer, and even to another answer which further adds value.

My understanding is that we should be editing the question and answer to provide a more comprehensive single point of truth, rather than making people read multiple answers and comments to get a full picture.

For example, on another question I asked I realized that I was missing a crucial part which was causing my problem. Zenbike had added an excellent answer on troubleshooting, based on the assumption that I did have all the parts. Rather than add another answer, I edited his answer to include the indication that a part was missing, followed by the troubleshooting tips.

What should be the edit answer/add comment/add answer strategy?

Answer 1

It's a good idea to edit a question if the edit adds something to the answer without changing the meaning of the answer. Examples of this would be fixing poor grammar, adding support or citations for the claims made in the answer, etc.

Commenting is good practice for asking for clarification, offering a dissenting view, sharing an opinion that doesn't necessarily add something, etc.

In the question about gears that you linked to, the first comment is disagreeing with the answer, or at least a portion of it. If the answer had been changed to reflect that, it could have undermined any upvotes that had been cast prior to the edit.

The second question that you linked to is a little grayer. Since you clearly indicated that the edit is an update, it's probably not a big deal. However, I think it would have been better to answer your own question, a practice that's perfectly acceptable on SE sites. This would better reflect the question and answer nature of our site. But again, in this particular instance I don't think it's a big deal one way or the other.