The text of comments (and other internal pages) does not get indexed by the search plugin.
Search indexes content passed to the postscan hook. Comments are inlined, but inline's speed hack avoids adding inlined content to the page until the format hook.
And hmm, that's somewhat desirable, because we don't want searches to find content that is inlined onto another page.
That suggests that the fix could be to call the postscan hook for internal pages.
However, the search postscan hook tells xapian the page url,
and uses urlto($page) to do it. And that won't work for
an internal page. Guess it could be modified to tell xapian the
permalink. --Joey