SES & Ralph,
That (# anywhere on the line will render anything following it as a comment) was the best answer for a one-liner but you can comment out an entire block of mod_rewrite code using the RewriteEngine on|off directive. Obviously,
# bunch of mod_rewrite code - enabled by the 'on'
any [B][I]mod_rewrite code[/I][/B] which needs to be disabled
# return to mod_rewrite processing
The only warning I can provide is that the RewriteEngine directive is specific to mod_rewrite code processing so don't use it to comment out Apache directives!
Yes, I get too focused on mod_rewrite but this is a very useful way to comment out mod_rewrite code.