For some random (nay, stupid) reason the Valve devs made the choice to prevent you from saving your game while in the developer "commentary" mode. This is how to fix that and enable game-saving:
1. Go into Options and enable the Developer Console
2. Start Developer/Commentary mode
3. Bring down the console (the ~ key)
4. normally you can type 'save [savegame]
' and 'load [savegame]'
but in commentary mode you get this message:
"*** REJECTING: myGame, due to map_wants_save_disable."
5. To enable saving, type:
You can now save your game. However, the standard save and load keys are still disabled. To avoid manually typing "save" and "load
you can bind those keys with these two simple commands:
bind k "save myGame"
bind l "load myGame"
6. You're done. You can now press k to save your game, and l (L) to load it.