Board Thread:Support Requests - Community Management/@comment-26327222-20160103161811/@comment-303594-20160103164815

This is part of what's called the hero image, and the syntax is actually part of the main page. You can see when people have edited it in the main page's history, for example: here.

I don't think it's able to be disabled, but anon users certainly can't edit it (I just tried).