Sites that use "Sign in" and "Sign up" to mean register and login should see their developers burn. Each time I select the wrong option, each friggin time.
@randulo I know the Dark UI patterns but those are the Idiot UI patterns.
@Ronflaix Often, the emphasis is placed on Sign up / register and users coming back can't find the login! In plain English, sign up and register don't have the same exact feel, though. The correct one may be context dependent. Register is always natural on a forum. Sign up for a mailing list. etc
@Ronflaix too late for me to try "Sign on" and "sign for" for april fools
@Ronflaix That is a constant irritation and the placement and emphasis of each plays a part, too.