I think this would technically be possible - not by deault though, you'll have to do it all yourself.
All questions, answers and comments use the same table, qa_posts, so you could fill in the tag field for answers as well. You'd need to add the field to the appropriate forms, and probably create a plugin to add the tags when the answer is submitted. And then some theme code to display the tags.
Check out the docs on the main site for more info on how to make plugins etc.