Comment alter taxonomy
This module will allow you to change the taxonomy terms associated with a node from a comment on that node. The module provides a set of permissions that allow you to limit this to only certain vocabularies, as well as to certain user roles.
The intended use of this module is primarily for allowing project issue nodes to have terms alterable via project issue comments, but this module does not limit this functionality to project issues.
At this point the module is still in development. It works, at least for the most part, but I am still tweaking the code and testing the functionality.