I think voting should definitely be kept anonymous for all of the reasons it is in the real world. The monastery is a peaceful place and I would hate to see that spoiled by a 'Monk War' sparked off by seeing someone persistantly voting you down.
The knowledge of who votes you up or down can/will affect your opinion of that person and how you react to them in the future. We could see a group of monks just voting for each others posts - which mould make a mockery of the XP system. I'm not saying everyone would behave like that but a minority probably would.
A better solution would be, as has been suggested, to send a msg to the author or post a reply if you think what you've got to say would be of interest to other monks. IMHO, a reply should only be sent if it contains useful information, not just a "You're great" or "You suck" message as this will just decrease the S/N ratio.