Why wouldn't it be "berøm" instead, because skuespiller is common-gendered? Is this adjective irregular or what?
As far as I know, "berømt" is the correct neutral term, so like other words that end in a "t" it remains the same either way, unless it's plural or definite. I'm really bad with the language terminology, so hope I make sense.
He's saying it sounds like the word should be common-gendered, not neuter, since the sentence uses "en" instead of "et."
I think Agent_Goodwrench is just saying that the word "berømt" ends in a t in it's base form, and so ends in a t no matter which gender it's describing (when it's an indefinite, singular noun)