The problem i see with this is that advice through the chat as well as through PM is very finite, it´s addressed to an individual and there´s no record of it available to anybody else. Good advice in posts is (in principle) permanent and can be accessed by anyone so it has potential to help an indefinite number of people.
While i certainly apreciate the value of advice given through any means, i feel perhaps reputation should focus more on contributions to the site in general (good public advice, interesting posts, advancement of available information, etc) rather than for a helpful chat with an individual.
Also, as a personal note, i´d be a bit wary of the value of reputation given by people too lazy to do a search for posts, if you know what i mean.
thank you!