I admit, I don't really use those buttons much, but my understanding is that they are used to modify the current (cursor) block element for the most part. Sure, they'll create a new tag pair if you're not already inside a block element, but how handy is that really? Gui-only users often use them to promote normal paragraphs to headers and demote headers to normal paragraphs.
“Politics: A strife of interests masquerading as a contest of principles. The conduct of public affairs for private advantage.”
Last edited by DiapDealer; 02-14-2013 at 11:38 AM.