The only reason to lock things would be because your userbase can't be trusted to behave responsibly—which, granted, is exactly the expectation of the average G

The only reason to lock things would be because your userbase can't be trusted to behave responsibly—which, granted, is exactly the expectation of the average GitHub user. In a well-run project, the bugtracker is part of the project's digital memory. This means that the appropriate thing is to cross-link the new bug and the old bug. Not doing so—or being unable to do so because the original bug was locked—makes triage and archaeology needlessly difficult. Say hello to selection pressure: you drive away the most valuable collaborators and are left with the ones that you're spending all your time trying to protect yourself against.