Coffeemakers are actually sort of a grey area. It doesn't explicitly say in the Residence Code of Conduct that you can't have one in your room, but amongst many CAs it is often interpreted that any small appliance must only be used in the kitchenette. Ultimately, it would be the decision of the residence managers who would instruct their staff one way or the other.
In the RCC, minor offence h would be the one that (kinda) covers it:
(h) cooking with electric frying pans, ovens, microwaves,
etc. within individual residence rooms; using halogen
lamps or humidifiers; using heating elements (electrical
or otherwise) other than those supplied by McMaster
University & Housing and Conference Services;
It's that "etc." that's the killer :-p
Now, whether or not making coffee is considered cooking, well, that's open for interpretation too (then there's that whole "heating element" thing - does it refer mainly to space heaters (which is the bigger concern) or can that be applied to something that heats water, too?), Suffice it to say that many students keep coffeemakers and kettles in their rooms all year without any trouble. If your CA takes issue with it, then they'd likely just ask you to move it to the kitchenette. CAs aren't typically power-hungry megalomaniacs just itching to cite you for every little thing :-p