What invalid HTML?

1. I know that html is the underlying format to the posts, but other users may not be aware of it, so the formulation is confusing for them.
2. more importantly; what invalid HTML was found? I did not use the HTML edit mode in that post. I might've typed in something which offended the checker, but it should've pointed out exactly what, and not just removed something without my knowledge and consent.
How hard it may be to understand that POSTS ARE NOT TO BE MUTILATED!!! (even if it may sound as innocent as removing noses from hand-written smileys).
JW
