ASOIAF: Why was Satin recruited to the Night's Watch?

We are never told his crime. WE know his background, that he was raised in a brothel in Oldtown in the Reach, yet apparently was picked up and sent to the Wall from Gulltown in the Vale.

This may be a mistake, a continuity error of sorts, on GRRM’s part, or he may have a detailed back story.

Some people theorize that he is Littlefinger’s spy; and that the fourth knife in the back from the unseen assailant in A Dance with Dragons is his. And, that, when Melisandre warns him against people he thinks are his friends but aren’t, she is talking about Satin. The evidence being that Gulltown is in the Vale of Arryn, where Littlefinger started his career and that Littlefinger owns brothels.
But then that doesn’t add up, since Bowen Marsh speaks against him so stridently. 

And, anyway,  I’m not certain if Littlefinger is all that concerned with Jon Snow, who is, until his unexpected acsension to Lord Commander of the Night’s Watch, pretty low down on the totem pole of Westerosi politics -- Satin arrived at the end of the first book...could Littlefinger have gleaned some information from Alliser Thorne when Tyrion kept him waiting for days that caused him to be interested in Jon Snow?? But no,  the timeline seems all wrong....

In my opinion, he is no more than he seems: a boy whore sent to the Wall for a crime unknown. Not a spy. Not a conspirator. And certainly NOT Jon’s lover. Genuinely loyal to Jon.

Written December 27, 2016