Hmm, I really like the idea of not being context-sensitive. Yes, just because PM has magic <code> tags doesn't mean it's the only solution to the ergonomic problem.

Having a single sequence that was used to delimit literal text, rather than configurable multiple sequences, would mean that a simple s/// operator would be able to find them.

In fact, if separate begin and end sequences were used, they could be turned into "<![CDATA[" and "]]>"respecitivly, and not need to grab everything in between. That would be very useful to operate as a simple filter of input.