is about right. The ampersand followed by some text then a semi-colon is valid Perl. It is also a valid HTML entity in some cases. So which will it be? Without forcing users to input special code tags in titles, there is no mechanical way to differentiate. This same problem does not afflict parentheses. So for this reason the change seems appropriate if it will alleviate concerns over mis-entered angle-brackets and such. Personally I'd prefer to turn on HTML encoding in posts and force users to use special markup for all HTML tags. That way I don't have to use code tags or HTML entities to type in a snippet.
FWIW, until now I'd never realized you even had a problem with this so-called "vanity tagging", nor was I consciously aware that we could now stop tagging our replies. I always thought those bullets were intended to be a cutesy/clever version of "vanity tags", not a protest against them. I mean, if I really wanted to be vain, I suppose I would have a sig with a link to my website on every post. I mean, how necessary is that? My login name already appears next to my post and I have a home node from which to do my advertising. No?