Comment 5 for bug 173415

One thing to keep in mind is that some of the Ubuntu bugs have multiple contexts (e.g. upstream inkscape and the Ubuntu inkscape package). The tags are attached to the bug rather than the bug in a particular context, so simply wiping all tags that are not Ubuntu-specific is a bad idea.

I am still interested in determining what problem you are trying to solve though. If adding a tag not found in Ubuntu's standard set to a bug did not affect the tags list for Ubuntu, would there still be a problem?

On the subject of encouraging use of standard tags, perhaps it'd be worth improving the UI to make it easy to apply standardised tags.