Re-edit: All IM services I know of support or once supported HTML in their profiles. Also, this isn't providing more HTML assistance, just properly connecting what LiveJournal has already documented.
These FAQs could be connected through Further Reading or with text in the profiles.
Re-re-edit: No, AIM does not support HTML proper in its profiles. However, it is possible to add a link (labelled or straight) with the Link button. I am not suggesting we document that, merely pointing out that it is possible to do what they are asking in AIM. The Linking profile does refer to the IM service's documentation, so if they start having trouble, they should go there. If they start thinking they can use HTML everywhere just because there's one link to a HTML document, that's their problem. They can't use all HTML everywhere on LiveJournal either, and not all of it consistently (entries, comments, entry titles). The only way they'll learn either one is testing, reading docs, or asking someone.