In reply to Bob.

If you’re looking at the actual staging site, it’s a migration from the Codex.

The Codex is freely editable by anyone with a WordPress.org account.

When editing is complete, we’ll likely have eradicated those spelling or grammar mistakes.

That being said, those work come from great contributions made by average WordPress.org users, developers, testers, designers etc alike. Some of them likely don’t practise English on a regular basis.

If you feel like you could contribute to the writing, ping me on Slack ? That is @kenshino

DevHub, Helphub, Codex and all parts of make.wordpress.org are created by volunteers. You could be one of them!