Maybe I'm in the minority, but I actually prefer the use "is comprised of" over "comprises". For the supposedly correct version, you can almost always say it differently:
E.g. simply: A proton contains three quarks. But if you want to use passive voice, there is no good other option. A proton is made of three quarks? Sounds too colloquial. ...is put together from...? No. I think "A proton is comprised of three quarks" is the cleanest way of saying what I want to say.
And yes, this was an actual example from my work and I discussed it through because I feel strongly about it :-)
Yes, for whatever reason "is comprised of" feels like a natural, abeit rather technical/formal, expression. It reads clearly, something I'd expect to see in technical documentation or an encyclopedia article or non-fiction book.
Whereas "comprises" feels halfway archaic when I read it, like it's the way an elderly British academic might speak, or something only used in legalese. Somebody using "comprises" in writing strikes me as a little odd, a little bit pretentious.
I'm not saying whether any of this is right/wrong, it's just the connotations I've absorbed.
I would object to the sentence "A proton is comprised of three quarks" on scientific grounds rather than grammatical ones. Only a tiny minority of the mass of the proton is in the three constituent quarks.
E.g. simply: A proton contains three quarks. But if you want to use passive voice, there is no good other option. A proton is made of three quarks? Sounds too colloquial. ...is put together from...? No. I think "A proton is comprised of three quarks" is the cleanest way of saying what I want to say.
And yes, this was an actual example from my work and I discussed it through because I feel strongly about it :-)