[coding123]

You need to tooltip it without underlines... Maybe you did but couldn't tell from your comment.

[ccooffee]

Without underlines makes the data even more hidden. The style looks nice and clean to expert users, but I don't expect any of my less-savvy users to actually find it. (Though I could be very off-base as I've never A/B tested tooltip hinting.)

[Izkata]

Dotted underlines are an old convention for "there's a tooltip here". Don't see it often anymore though.