(a) Has nothing to do with Vector, happens with all skins.
(b) I said long ago that >|< alignment sucks in Special:Preferences, I'd prefer left-left, and have overridden this in my personal styles.
(c) There is more than one issue in this bug.
(d) a) is because Xml-functions are used. They do not allow any kind of mark-up, and this is known and no fix is currently being implemented.

Changing to Preferences.

Andrew, is this a regression in html support or just some custom message formatting that wouldn't work?

(In reply to comment #3)

(a) is an alignment problem, which I do not know to fix with custom CSS (besides the fact that my personal fix woun't help others)
It is also an instance of the fact that translated messages are usually longer than you think.

(b) is yet another issue of the fact that proper language tagging inside some translations is needed - outlined in http://www.mediawiki.org/wiki/Internationalisation#Expect_untranslated_words - and the XML function does not currently allow it, as Niklas pointed ot. If this is seen as good way to do it, I am willing to e.g. add a "let markup pass" parameter to those functions that need it, but I am far from convinced that, making message treatment more complicated was desirable.

Resolved in r53800 (was regression in r53173).