Once again just sharing my own thoughts and perspective on this. The term "Straight Acting" has two meanings, depending on context:
a) "Straight Acting" may refer to acting straight in order to hide one's homosexuality.
b) "Straight Acting" may refer to possessing more masculine traits that are contrary to the stereotype of the effeminate homosexual.
I think the major issue is misinterpretation: depending on the context you use it in, both of them make sense, however I personally avoid saying "straight acting" in the context of definition "b". The reason I would avoid using it, is because it relies on the stereotype that the average gay man is effeminate. You know the stereotype: that skinny-jean, pink-shirt wearing, hair-product using, clean shaven, high-voiced lean guy who bends his wrist at a ninety-degree angle while saying, "girlfriend!"
My own preference is to use the term, "masculine" when referring to a gay person who is not effeminate, that way I deal with the stereotype while not reinforcing its existence. The definition I use for "masculine" is: "...having qualities or appearance traditionally associated with men, especially strength and aggressiveness." It says nothing about sexuality--it only deals with physical or personality traits. To summarize, my thoughts:
1) "Straight Acting" is a term used to identify one's self as concealing their homosexual nature.
2) "Masculine" is a term used to identify one's self as not possessing effeminate qualities.
Context is important, and everyone has their own definition when it comes to contextually-specific words and phrases like this. When I read someone's profile, and they say they're "Straight Acting," I do not use my definition of "Straight Acting". Instead, I read their profile, and try to deduce what they mean by "Straight Acting", and then I use their definition.
It's a case-by-case issue, for me. But if we could establish a standard meaning for the term, it might be easier, as there'd be less confusion on the whole issue. Hopefully.