Just to share my thoughts:
In the past, MS Office 2010 and 2013 used to be very good in grammar suggestions.
Years ago, when I had two jobs and worked for a university, they gave me a licence for Office 2013 Pro and it was very good in the suggestions and explanation of the rules.
When I stopped working for the university a couple of years ago or so, I uninstalled 2013 and bought a subscription for Office 365 since it was more affordable.
Needless to say that (I have only tried the Home edition) it is very bad in the grammar suggestions... it flags all text saying "replace formatting with style 5 blah blah style 7 blah blah"... it flagged my entire PhD thesis and I am unable to check the grammar.
Yes, I had the thesis "ready" months ago, but the supervisor always has new ideas and I have to implement them.
So, I am revising the thesis using LanguageTool which is far more powerful than Office Home 365's (haven't tested the "Pro" edition since it is too expensive for me).
I would like to thank @tiagosantos for joining our team... at first I was apprehensive, if you all remember, but it was the best thing for the project... I can now add a rule now and then knowing that a ton more are being worked on by him.
I am involved on too many projects and sometimes I dedicate full time to one or another... for example, in the last few days I was working on Proofing Tool GUI and implemented some useful features, one of them suggested by a user a year or so ago.
Thank you my friends for the best grammar checker around! I am very proud to be part of it.