4 stars because:

1. When I comment a tactic, I have no way to see if my comment wad answered
2. I constantly get tactics, which I have solved already
3. No tactic filtering, it would be cool to filter by tactic rating, type (opening, middle, end), attacking/defending etc
4. No castling support

Good job so far anyways!

anya_tikanova about Chess Tactics and Lessons, v2.1