@panaghiotisadam use it from time to time on sites that have really small text, but quite truthfully I don't think too many people even know it exists. A while ago, I had somehow set my browser down two sizes on the text and didn't realize it. I had certainly not done it on purpose, that is why I suggested checking it.
@drlisab, it seems that sometimes some of the code remains in the post, so if you copy it all out and then paste it back in, some of the code is still there. What you can do is to delete the post and then recreate it again, not using Word, and then backdate it to the date and time of your original post.
There is also a button (looks a little like an eraser) on the toolbar which will supposedly remove all code from a post. You might try opening the post, selecting everything in the post, and then clicking that button and see if it will fix the issue. I've had spotty luck with it, but sometimes it works.