I'd say that with a good heuristic, make codetag checks MANDATORY for Anonymous posters (as they won't be able to edit after they submit), and an OPTIONAL FEATURE for those who have logged in.

Of course, I've already mentioned that I think this site should use a format that's closer to POD and Wiki writeup, rather than this mis-mash of HTML and Everything2. Stuff that's indented should be code/pre, and maybe a little heuristic to absorb immediately neighboring lines which start with curly braces or known sigils or keywords.