In the very short term maybe, but in the longer term not pissing professors off is also useful.

Sometimes. I was drawing assuming that in a first year philosophy subject the class sizes are huge, largely anonymous, not often directly graded by the lecturer and a mix of students from a large number of different majors. This may differ for different countries or even between universities.

As a rule of thumb I found that a social relationship with the professor was relevant in later year subjects with smaller class sizes, more specialised subject matter and greater chance of repeat exposure to the same professor. For example I got research assistant work and scholarship for my postgrad studies by impressing my AI lecturer. Such considerations were largely irrelevant for first year generic subjects where I could safely consider myself to be a Student No. with legs.

I don't think Penrose's hypothesis is so obviously-to-everybody absurd (for any value of “everybody that includes freshmen) that you can just laugh it off expecting no inferential distances.

You are right that the inferential distance will make most students not get the humour or understand the implied reasoning. I expect that even then the behaviour described (laughing with genuine amusement at something and showing no shame if given attention) to be a net positive. Even a large subset of the peers who find it obnoxious or annoying will also intuitively consider the individual to be somewhat higher status (or 'more powerful' or 'more significant', take your pick of terminology) even if they don't necessarily approve of them.