Regarding 1, from a quick look at the code my understanding is that course custom fields aren't included in the search either, although Amir is saying "The search works well on course custom fields content in my experience" which would contradict that - unless he's talking about report builder filters on the 'Courses' report source? I will expand the enhancement ticket to include custom fields as well as tags.

Regarding 2, I think that's referring to user profile custom fields, not course custom fields. User profile fields have the "Display on signup page" option.

Simon