Well, it definitely is one, but you seem to mean "a conspiracy theory in the sense often depicted in mainstream media: unsubstantiated paranoid ramblings, see also: tinfoil hat".
I mean, it is unsourced, but it's not an unheard of idea, and should be quite Google-able. Microsoft has engaged in astroturfing many times (last in 2014 AFAIK) so it's entirely possible.
NeoGaf discussion with a list of news reports on MS astroturfing:
(I'm not associated with NeoGaf, I found it on Google, I vaguely recall it having some GamerGate-related stigma attached to it so I added this disclaimer)
I mean, it is unsourced, but it's not an unheard of idea, and should be quite Google-able. Microsoft has engaged in astroturfing many times (last in 2014 AFAIK) so it's entirely possible.
NeoGaf discussion with a list of news reports on MS astroturfing:
http://m.neogaf.com/showthread.php?t=579641
(I'm not associated with NeoGaf, I found it on Google, I vaguely recall it having some GamerGate-related stigma attached to it so I added this disclaimer)