I've been endorsed by a number of people I have worked with, for my apparent skills with Solaris.
I have worked on solaris for about 3 months about 9 years ago during a career of 17 years (and counting) it's not a skill I added to my profile myself, someone else endorsed me for it and it appeared.
Now I'm not saying I'm not good at it, but I'd have thought that the people who have endorsed me would know what I actually have worked on when I work/worked with them.
I can only speculate they're confusing Solaris with SuSE Linux.
I prefer the written endorsements, particularly when I can say mine are all unsolicited and not reciprocal.