I am all for an "auto-parse" option on the server side (please, do not assume everybody has Rikaichan/kun running: awesome as it is, it only supports a small subset of browsers and I don't think it is the place of SE to tell the user what browser they should be using). It is doable but frankly unlikely at this stage...
In the meantime, perhaps the FAQ could be amended with a short "best practice" recommendation on providing kanji reading. Of course we would first need to come to a consensus, which might not be easy ;-)
Personally, I like the form: 漢字【かんじ】
(death to romaji!) for single word mentions, but I have seen many people use 漢字 {かんじ}
in questions, and it looks OK too (perhaps easier to type for beginners?).
For what it's worth, HTML already has a specific tag to display furigana (or equivalent) in Asian languages:
<ruby>漢<rt>かん</rt></ruby><ruby>字<rt>じ</rt></ruby>
which is meant to look something like:
かん じ
漢 字
(with better spacing, of course)
It will display nicely in most modern browsers (including IE, I think). With a bit of extra CSS, it will also display fine on less modern ones.
Unfortunately, SE currently doesn't support the <ruby>
tag and strips it from submissions. But I suspect it will be much easier to request they allow it (and perhaps even provide a tool or code shortcut to make its writing less cumbersome) than to have them auto-generate furigana.