This was a bit of a hot topic between me and my friend so I'd like more opinions on this. Some people like putting a stick of cinnamon in their tea but I find it just tastes weird. Just me?
Cinnamon is often a big component of masala chai, so I don't see anything particularly controversial about using it in tea as a sole spice. I can see it working with a heavy, malty tea like Assam, especially if made "Indian style" with simmered milk and sugar.
Masala Chai is delicious. In the middle east, most teas have a single added spice such as cardamom, bergamot oil, and mint in the case of Moroccan mint tea, as well. Sure China and Japan don't like adulterating their teas but they have a sudo-religious relationship with tea that has many strict rules.