==== What is the problem?
If a user is partially blocked from the page "Foo" they cannot add a tag to a revision on the page "Bar".
They are also prevented from doing any actions on Special:Tags.
In both cases they are shown a message saying they are blocked.
I am assuming that we only want to prevent a user from tagging revisions on pages and/or namespaces they are explicitly blocked from and that partially blocked admins should still be able to create/edit/delete tags. Of course, you can decide what you think is appropriate.
For more technical information see, for example, T209004.
From reading the code I belive the same is true of the API for this component, but I have not tested it.
==== Steps to reproduce problem
On a wiki which has partial blocks enabled (e.g. https://en.wikipedia.beta.wmflabs.org or http://test.wikipedia.org/)
1. As an admin, go to Special:Block
2. Partially block $user from page $pageA (screenshot below) (make sure $user has changetags rights)
3. As $user, go to page $pageB, view history and attempt to tag a revision
**Expected behavior:** Behaves as if the user were not blocked, i.e. they can add a tag (assuming this is what we want)
**Observed behavior:** User cannot add a tag, is told they are blocked.
Similarly, as a partially blocked admin (or someone with managechangetags rights), go to Special:Tags and attempt to create a new tag.