If I have a sense or feeling or, heaven forbid, absolute knowledge that questions or answers are wrong, equivocal or misleading, I "drift off" if by that you mean stray from a concise and direct reply or comment.
Let me give you three examples from today's forum.
"oye como va". The question title and question body differ from each other. The question had been asked before. There was conflict in the replies. My answer is supportive of only one of the conflicting replies. I was a little loquacious. However, I thought it best to defend my position with supporting material and explanations.
" 'Sea Lion' in Spanish". There were two answers. Both of them correct. It was necessary, at least in my mind, to state that both answers are correct.
"How to say 'credited' in Spanish". I had a sense or feeling that the word sought, i.e. 'credited', was not the appropriate word for the job. While I could have answered exactly what was asked, I chose to suggest an alternative word in English and the result is a different word in Spanish than the one that was asked for.
Sometimes, it's necessary to play the role of sheepdog and to bring things back into the fold, so to speak. Sometimes a question or reply is not clear. Sometimes a respomder has clearly misunderstood the question and given an answer from left field when something closer to home base was appropriate.
There are many reasons why answers might seem to "drift off". We can only hope that such departures are warranted.
By the way, GeofC, I liked your reply to "Calíope" because you explained how others could do what you did to get to the answer thamselves. That kind of information helps both the questioner and any other member who may see and follow up on your reply.
Oh dear. I'm headed for the same practice as IZanoni, too wordy. Shut me up.
Muchos saludos/Best regards,