Yeah, his name turned out to have something going on with it – his chat name had a capitalised first letter, however BTTV showed it as all lowercase whenever I was highlighted by him. I got him to check his display name in his Twitch settings and that was all lowercase too, but his display name in chat still had that capitalised first letter. I guessed that it probably had something to do with when he created his account (back in 2010) and Twitch may have automatically capitalised the first letter of all names before implementing the display name option. Anyway, after he modified his name in the display name box in his settings, it started working. Thanks!