I am. Links posted above. In HTML5 all 4 elements have specific meaning.
<b> is less memory used over <strong>
I'm going to refrain from making a diplomatic comment on that one. ;)
I don't know of a WYSIWYG Editor that allows you to use all 4. It's either <b> and <i> or <strong> and <em>. With WordPress, it's <strong> and <em>. A true browsing nightmare for anyone using screen reader/speech browser software. Ya, I know, who uses that stuff?