I frequently see lots of threads on here with no responses.
I don't know, since I am new here, but I was told a lot of the core knowledgeable members had chosen to leave here. <shrug>
I will say that boy animals sometimes just let their junk hang out, sorry, just is what it is.
I doubt highly it's anything sexual--your rat knows you're not another rat ;D
In short, I wouldn't worry about it, unless or until you start seeing really over-the-top hormonal behaviors, in which case you may want to neuter him.