I was unaware that the

 

:indent

 

markup actually used DL/DD tags. That's an awful idea. It should either <blockquote> or <div style="margin-left: 1.5em">.  Changing that immediately would have no adverse effects.
 

The definition list conversion should only happen when you begin with a semi-colon:

 

; definiendum : definiens

 

As for the thread's main question, I agree that wikitext should parse more intuitively - but this would break current pages. Currently, HTML is actually allowed inside wikitext - we can't escape it.