It is my opinion that this should be handled by servers/games. Servers/games can output a chat message warning as needed, but script API might be lacking. Having this hard-coded in client puts undue burden on game designer as players will get erroneous messages if game does not penalise 50% weight or penalises it differently.
There already exists the overweight effect: yellow weight at 50% and red one at 90%. These are completely server/game-controlled.
I propose removing the in-client overweight handling or at least disabling that warning pop-up by default.
The notification in question:
Resolved: asuratva had a great idea to just switch the warning to a speech bubble, which does not interfere with gameplay. In this form and at present server-side implementations I am in favor of keeping the warning. N.B. Herc also has a packet to set % at which this warning appears, and 100+% disables it.