Ok, I've put the topic back on the table.
Due to CG non-optimal technical architecture, adding optimization flags would greatly impact the duration of submits since we recompile your code for each battle. Granted, that sounds a bit weird, but it is how it is.
That being said, we're willing to dive into the code and change this. I'm sure you'll concur that this won't be the easiest nor the safest fix of the year. It'll take a bit of time. Considering our current priorities, I'm confident we'll be able to tackle this during summer (vagueness intended).
Meanwhile, since there are only a few users coding in this language, we have activated release mode for Rust for submits in multiplayer games (only games with last battles).