Feature summary (what you would like to be able to do and where):
Convert uppercase HTML tags in signatures to lowercase.
Benefits (why should this be implemented?):
The syntaxhighligher doesn't recognize uppercase html tags and colors the syntax in red (for broken syntax). There might be other tools that don't work correctly with it. Making all tags lowercase standardizes this without too much work.
Why only signatures? HTML tags are not only in signatures. Also, what about signatures that are already on pages? Converting them as well would be quite some effort. I think it’s easier to just make your syntax highlighter (whichever it is) standards-compliant by it recognizing uppercase tags.
Yeah, uppercase tags are valid-and-functional HTML. Whatever tool you're using for syntax highlighting should accept them.
(DiscussionTools itself doesn't do any syntax highlighting in source mode, so I'd need more context to know which tool isn't handling said tags correctly.)