Red Hat also has patents and the wording of the promise is nearly identical to the one of MS, I'm quoting RH:
http://www.redhat.com/legal/patent_policy.html
"""
Our Promise with Respect to Software Patents We Hold ...
Our Promise:
Subject to any qualifications or limitations stated herein, to the extent any party exercises a Patent Right with respect to Open Source/Free Software which reads on any claim of any patent held by Red Hat, Red Hat agrees to refrain from enforcing the infringed patent against such party for such exercise ("Our Promise"). Our Promise does not extend to any software which is not Open Source/Free Software, and any party exercising a Patent Right with respect to non-Open Source/Free Software which reads on any claims of any patent held by Red Hat must obtain a license for the exercise of such rights from Red Hat. Our Promise does not extend to any party who institutes patent litigation against Red Hat with respect to a patent applicable to software (including a cross-claim or counterclaim to a lawsuit). No hardware per se is licensed hereunder.
Each party relying on Our Promise acknowledges that Our Promise is not an assurance that Red Hat's patents are enforceable or that the exercise of rights under Red Hat's patents does not infringe the patent or other intellectual property rights of any other entity. Red Hat disclaims any liability to any party relying on Our Promise for claims brought by any other entity based on infringement of intellectual property rights or otherwise. As a condition to exercising the Patent Rights permitted by Our Promise hereunder, each relying party hereby assumes sole responsibility to secure any other intellectual property rights needed, if any.
"""
They promise not to sue you just like Microsoft. I guess it's perfectly standard legalese then if two companies as far away as MS and RH use the same wording.
Now the RH promise is limited to software with a limited set of licence (they can add to it) while MS one is limited to some implementations of a standard.
I'd say that if a patent troll buys MS we're safe, but if a patent troll buy RH and the FSF needs to publish GPL 3.1 or 4.0 we're screwed since RH promise does not cover future licence.
IANAL