This question already has an answer here:
I was recently on Stack Overflow answering a question about why someone's CSS was not working.
The question had only one tag, and may not have been top quality, however I started answering it.
Having spent about 10 minutes constructing an answer explaining the fault was elsewhere, and giving some tips to try and find it, I submitted the answer, only to find the question had been deleted whilst I was answering.
What I would have found useful is a feature that, when viewing the question, and certainly when deleting it, shows how many (if any) users are currently answering the question. Apart from the obvious effort of implementing a Stack Exchange wide real-time tracker for answerer's on both mobile and web, what would be the objections to such a system?