Freshen and fix formatting for some comments used in generated documentation (#2462)

## Context

These comments are used in documentation published at
https://support.getgrist.com (via
https://github.com/gristlabs/grist-help repo). The change fixes
formatting, improves clarity, and in case of a broken link, updates it
to what `grist-help` already uses.

## Has this been tested?

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- [ ] 👍 yes, I added tests to the test suite
- [ ] 💭 no, because this PR is a draft and still needs work
- [x] 🙅 no, because this is not relevant here
- [ ] 🙋 no, because I need help <!-- Detail how we can help you -->