1. It's against the rules of chess to write anything other than a game score, during a (live) game of chess.
2. You play mostly blitz and bullet. How do you think you'll have the time to write contemporaneous notes?
3. Most speed chess is unworthy of notes or serious study.
Here it was pointed out to me that the "notes" tab is only available for online chess. Why disable note taking in live chess? It would still be a useful feature for post-game analysis.
As things are right now, keeping track of one's comments on live chess games would have to involve PGN's, third party software or commenting with an annotation. It would be nice to have the feature integrated.