Quote from Jason's comment in #6708:

Not for this PR - but the result of this format call is typically thrown away. It should be possible to check if methods like WriteVerbose will do anything before formatting, or at least add overloads that do the formatting only after deciding the formatted string is needed.

We could add a few overloads to WriteVerbose and WriteWarning, which take a format string and arguments. So we can defer the construction of message until we know for sure we are going to write out verbose messages.

Open this issue to track this investigation.