However there should be a different rule, i.e. one answer per question per user, which is applied only to new (i.e. low-reputation) users (the existing behaviour for higher-rep users would be unchanged):
- Because new users are less likely to do it well/appropriately
- Because new users may be trying to spam the question: i.e. to provide more than one unwelcome answer.
This new rule should be applied, even when their first/original answer to the question is deleted (instead the user may edit their deleted question, and then reopen it or flag it for a moderator to reopen).
Although there's no great demand for feature its justification is that I'd guess it's trivial to implement (not much need but even less cost to implement): because there is already a message box displayed, when multiple answers-per-question-per-user are detected.
There are many other automated features which help keep the site tidy: the message box for repeated answers; inviting user to Chat instead of having long comment-dialogs; the ability to "protect" specific questions; etc.
Also this (automated) feature would less intrusive to new users than protecting a question: because "protection" prevents every new user from even answering the question once.
I doubt I can establish whether there's "enough misbehaviour from new users to justify this feature" without without access to statistics re. deleted answers; and even then, whether that's "enough" new users would be subjective.
Yet seems to me self-evident that one answer per question is usually enough, that multiple answers per question is an exception not a rule, and that only allowing established users (who have e.g. a rep of 10 equivalent to "remove new user restrictions") to escape that rule would not be unduly restrictive.