I don't know, and never tried to see if MAC address is tracked.
Many people want an extra account to post anonymously (if they are using their real name) or for a business pursuit, or sometimes to vote for themselves... but my post is addressed to many people that simply can't get a first account for themselves.
I assume a computer or phone is very personal; most people will have a unique MAC, but likely share an IP address with another Steemit user.
Also, this is not a manual on how to hack the steemit signup process (which I believe will change very soon); it's letting people know to try it again after taking reasonable measures to dissociate themselves with another user they may share a connection with.