You could argue that "pleasure" is a broken word, that brings up associations that are usually useless or distracting in the context of other things categorized by that word. But it's clear what the word refers to, so people can well use it.
You'd need to make a case for its usage leading to incorrect inferences. Given the sequence on words, this discussion must be held to a higher standard.
By saying that there is no such thing as pleasure, I don't mean that I don't enjoy anything. I mean that I can find nothing in common among all the things I do enjoy, to call "pleasure". In contrast, I can find something in common among all physically painful things. I have experienced toothache, indigestion, a stubbed toe, etc., and these experiences differ along only a few dimensions: intensity, location, sharpness, and temporal modulation are about it. I perceive a definite commonality among these experiences, and that is what I call "pain". (Metaphorical pains such as "emotional pain" or "an eyesore" are not included.)
However, I cannot find anything in common among solving an interesting problem, sex, listening to good music, or having a good meal. Not common to all of them, nor even common to any two of them. There is not even a family resemblance. This is what I mean when I say there is no such thing as pleasure. But that's just me. I know that mental constitutions vary, and I suspect they vary in more ways than anyone has yet discovered. Perhaps they vary in this matter? Are there people who do experience "pleasure", in the sense in which I do not?
Why is this a LessWrong topic? Because people often talk about "pleasure" as if there were such a thing, the obtaining of which is the reason that people seek pleasurable experiences, and the maximisation of which is what people do. But it appears to me that "pleasure" is nothing more than a label applied to disparate experiences, becoming a mere dormitive principle when used as an explanation. Does that difference result from an actual difference in mental constitution?
If there are people who do experience a definite thing common to all enjoyable experiences, this might be one reason for the attraction, to some, of utilitarian theories -- even for taking some sort of utilitarianism to be obviously, trivially true. My experience, as set out above, is certainly one reason why I find all varieties of utilitarianism a priori implausible.