_underline_ works but not __underline__

[spenserblack]

I can't say it's unintended behavior, not because it's different from my intent, but because I currently have no intent.

Should __underline__ be equivalent to _underline_ and render as [u]underline[/u]?

Pros

• The double underscores looks good.

Cons

• The double underscores might give the impression that it follows similar logic as * and ** (the more you use, the "stronger" the emphasis is)