Some people also begin e-mails with "I am ..." even though it's in both the From field of the message and at the end, two paragraphs down.

Some people also begin letters (like cover letters on job applications) with "My name is ..." even though it's at the bottom of the page.

Bottom line is that some people don't think about how their communication comes across. Maybe they just enjoy seeing their own names a lot.

Regarding FT and other BB posts, some people sign their real names but have handles that are totally different. (Several examples come to mind.) I can accept that; the signature adds content. Signing with the same handle that is already to the left of the post is a waste of two lines, often multiplied when others quote an entire post and don't edit out the parts they're not referring to.