7->T is definitely the most oblique of the four numbers. I'd say that 0 as O is completely unobjectionable, and 1 as I mostly so. It's a lot easier for me to read #c0ffee than #7a57e5.
He makes a direct reference to leetspeak [0] which has leet/1337 even in the name. As someone who grew up alongside gaming, the T/7 connection is acceptable without issues.
