Hi Harry,
When you want to apply two sets of tags to a word, you have to reselect the word before clicking the button. Say I wanted to make it bold and blue, I would have to select the text, click the bold button, but then it gets deselected before I have the chance to make it blue. IMO, it would be better if, when you clicked a button, both the word and the new tags get selected, so they can all be wrapped in new tags :)
Great work though!
Tom