You're going to have a hard time convincing anyone that women would have sex with RMS, let alone have sex with him on a mattress on the floor of his office. Jokes aside, this sounds downright unprofessional. I would have expected the institution to put this kind of behaviour in place.
considering according to https://news.ycombinator.com/item?id=20991909 he apparently was homeless and lived out of his office for a while, yeah that's probably the definition of unprofessional.
That seems like a real stretch from having a mattress on the floor of your office. Still not seeing the “implication” here.
the implication is that he slept in his office. Common among hackers and people with a passion for computing, also 1970's