General rules that you use for strangers don't really apply to anyone you have a personal relationship with. And sexism is usually a problem of power mismatch between the two people, which doesn't really apply here either.
Thanks for your reply. I don't know these people and don't know their history. My opinion is that their comment should be clearly non-sexist or clearly relevant.
Captions are often descriptive of what is actually in the picture, not merely the most relevant thing in the picture but also incidental details.
It just makes it irrelevant. The website has a long-running relationship with Sebastian, who only recently developed a beard. The adjective was highlighting the novelty of his appearance to a readerbase that is more familiar with a depilated Sebastian.
In short, your criticism would have been valid in many circumstances, but does not really apply to this specific caption.
Thank you for your reply. I just didn't get the joke - that makes it a bad joke IMHO. Its the kind of comment that condones irrelevant body references that distract from the point and would likely suppress discussion if the subject were a woman. My point is that we need to get out of that habit entirely.