I recall hearing some advice about avoiding question marks in page titles. Is this well-founded? What are the issues, and what are the workarounds.

One possibility that I could imagine are problems with the question mark in the URL string, leading to invalid http requests. Another is that certain parts of the code, e.g. search, interpret the question mark as part of a regular expression.

I can’t think of a reason why question marks in the page name would be a problem. The name is CGI-escaped when forming the URI.