"They use the same nickname for their computers, Marcan hosts some infrastructure for Lina and they have similar preferences for how to set up KDE" could of course mean that they're the same person...

Or it could mean that they're close friends? Seems like extremely weak grounds to go around claiming with certainty that they're actually the same person. Hell, I have people in my life which this would almost describe: people whose Linux system I helped set up and whom I host infrastructure for.

Could they be the same person? Sure! But why the hell are people going around confidently stating that they absolutely are, based on such weak evidence? If my sister had stuck with Linux when I helped her install it some years ago, you could literally use the same evidence against me.