I vote no on this one - maybe have it accept <c> and </c> as alternate shortcuts, but having <> mean <code> and whatever the tag would be, either <> or </>, for this main reason.

I've seen snips of code that look like this - having someone post code snips like these without wrapping proper code tags around it would have these snips show up incredibly funky.

print "How can I serve you, oh master? ";
my $input = <>;

while (<>) {
   # Stuff here
}
[download]

See what I mean? Bad stuff there, as it'd turn the rest of the post into a giant code tag.

~Brian