Adding a comment block to two different pages within the same module result in the same comments being displayed

This is easiest to reproduce using an activity like lesson which has multiple pages:

Steps to reproduce:
1. Create a lesson activity with 3 content pages.
2. Preview the first lesson page and add a comment block to the page.
3. Add a comment to the comment block that says "First Page"
4. Preview the third lesson page and add a comment block to the page.

Expected result: You should see an empty comment block
Actual result: the comment block will have a comment that says "First page"

See: https://moodle.org/mod/forum/discuss.php?d=316647#p1269893