In WYSIWYG editors, when you select some text and try to format it as a heading the whole paragraph turns into a heading, rather than just the selected text. With all other elements (bold, italic, etc.)—granted they're inline elements but I don't think the average user know what that even means—the opposite happens.
I don't get this.
It seems that this is the most used (if not the only) approach used, but as a user I don't think I'd expect this behavior at all.
My question is: why are WYSIWYG editors implemented like this, and isn't it true that an average user would expect only the selected text to turn into a heading, rather than the whole block-level container?
I also made a video show the difference between the two approaches: https://vimeo.com/87710823
Any input appreciated.