[cestith]

I see a typo.

You do not get to choose when a writer uses a contraction. You might expect that I'd have used "don't" there, but the simple truth is people use the full words even conversationally sometimes. This is especially true when they want to emphasize the "not" part of a phrase like "will not", "would not", or "do not". Your suggested edit changes the meaning of the parent post a shade.

Where's the mixed metaphor? You may be able to sell me on "weird gate to keep" being a trite metaphor or perhaps even an awkward metaphor. What's mixed about gatekeeping, which seems to be a single common metaphor?

If this is the quality of editing the tool offers, one may wish to stick with spellcheck. Encouraging a particular organization's writing style within that organization can have some nice effects, but you don't get to determine everyone else's writing style.