Microsoft grammar checker

In my previous post, I hinted at the inaccuracy of Microsoft Word's grammar program. I wrote that after complaining so much about wordiness, it failed to detect the genuine subject-verb agreement error below:

(1) The quality of these voices matter.

As we pointed out, the correct verb is matters.

It was a relatively simple sentence, yet the mistake went undetected.

Though I have never used any grammar checker for my writings, except perhaps to check for spelling, my interest was nevertheless piqued.  How accurate or reliable is the grammar program? I wondered, and decided to test it out.

Microsoft Word 2010 Spelling & Grammar: English (United Kingdom)

A total of 12 error cases were used in the test. The last case, sentence (12), was deliberately chosen and positioned to verify that the grammar checker had not stopped working after sentence (4).

For anyone not familiar with Microsoft Word's grammar checker, the green squiggly line indicates a possible grammar mistake. The corrections in red were added by me after the check was completed, using a separate graphical software so as not to confuse the grammar checker. 

Though it was only a limited test with contrived sentences, the result has nonetheless revealed the vast inadequacy of the grammar program. Many of the straightforward, non-tricky error cases passed the check without a single complaint. For being such a nag over perfectly fine structures such as passive and cleft constructions, it cannot even reliably handle rudimentary mistakes.