Simplify ignorance and other annotations handling

[Martoon-00]

Clarification and motivation

The code in Markdown scanner that handles annotations is complicated and hard to work with. And we are planning to extend that even more (for redirects, for copy-paste protection checks, e.t.c).

I very much want us to simplify that code before adding any new features, because otherwise, that will be a path of bugs and pain.

Acceptance criteria

• We discussed how to better simplify the code.
• The refactoring took place.

[Martoon-00]

We are discussing this in Slack.