I don't reject HTML email, but I always have my client set to read plaintext. 99% of the time, the worst thing that occurs is simply some garbled hyperlinks for a verification email or similar.

Personally, I don't have any need for HTML email in my daily life, and the only emails I occasionally get that are very obviously 'broken' in some way in plaintext mode are usually marketing emails or other messages I don't want to read in the first place.

So, I figure, may as well keep it disabled since plaintext is more consistent and easier to read, and there is significantly less surface area for exploits when you don't need to bundle half a browser to view a couple of paragraphs.