Ah yes, I too remember when COMODO was ripped out of browsers in 2011 when it came to light they gave sign-anything rights to a bunch of resellers, one of whom was hacked. And then again in 2016.
And another fun one unrelated to signing was when they tried to trademark "Let's Encrypt" in 2015.
But yes, it is not a common issue and effort would be better focused on improving site security in other ways. (unlike the rest of my comment, this line isn't sarcasm.)