I was simply typing a comment in an issue (JRA-8165) that had some characters like underscores or plus signs, as one might do when describing an issue. Unbeknownst to me, these are text effect "tags" in the new wiki markup scheme. That just won't do. If I explain that an error occurs when a user types in

"_xxx_"

, I want to see the actual underscores in the issue description, not an italicized version of what's in between them: "xxx". HTML tags work because
1) the tags/codes are not likely to be used in the normal course of typing
2) they are ways to escape them if necessary, but only a programmer would ever need to know how to to that
In what is being presented here within JIRA, a casual user would not likely try to figure out how to get around the automatic formatting. It may be unlikely for an issue description to have phrases like noformat, but underscores, dashes, plus signs, and even curly braces are extremely common and are not suitable as tag markers in my opinion. I can easily think of when one might have an issue that gives code snippets like

code

and these should not present errors.