That's why the only useful rule is not to use it if you're in any doubt whatsoever. And if you're not in any doubt whatsoever, you can write down the actual rule, right? The one that covers all situations? No? If not, just don't use
whom. Ever. Because it's never necessary except in fixed phrases, like
To whom it may concern or
For whom the bell tolls. Anybody who thinks it makes you sound ignorant is giving themself away as clueless about language. So ignore them. —
John Lawler Oct 11 '13 at 2:57