First, the red warning text that appears in some places (like the edit preview)
should always be properly done with CSS. (Aside from simple correctness, see
feature request [[989]] for a reason.) I'll suggest <class = "warning">.

But this only works in system text. Red warning text is also used in wiki-edited
text (see the top of [[w:en:Donations for victims of the 2004 Indian Ocean
earthquake]] for an example). So we should have a wiki markup for it. I'll
suggest "<warn>...</warn>", and if anybody objects to that on the grounds that
wiki tags shouldn't look like HTML tags (as <nowiki> does), then I'll let them
suggest an alternative ^_^.

Version: unspecified
Severity: enhancement