it will affect the esc?
i thought it just blocked the reverse current flow
I guess it was a hint towards the current regeneration scheme, but nobody can really say if it will hurt anything (apart from not getting regen. of course, but this loss is fairly negligible anyway if you go more than you brake), unless they have the schematic and some measurements to back it up.
However, there's other reasons for not just plugging a diode in series with the battery, like the voltage drop of the diode and the price if you wanna minimize that drop.
if it wont work for me, what other options do i have to prevent it?
The obvious one: Use a polarized connector and stay on your toes while you mount it to the battery and the Sabretooth - then never remove the wires.
Use a similar (correctly polarized!) connector on the charger.
Another option would be a fuse in the positive line and a reverse biased 40+A diode to blow the fuse if reverse polarized, or (perhaps cheaper and certainly faster reacting per $$) a 40+A SCR controlled by a small diode (eg. 1N4148) and a resistor.
Here's how it would look with a 40A diode...
(B+)---[Fuse 40AT]---+---(+S X25)
If the battery's reversed, the diode will conduct (keeping the voltage down to around -1V to -1.5V until the (much slower) fuse is blown.
The insertion drop is just that of the fuse and you need a fuse anyway, so you just add a diode (or SCR, small diode and resistor) and get no further voltage drops.
Quite amazing that they haven't incorporated some protection themselves, instead of just writing a warning in the manual and wiping it off on the customer - at that price and considering how easy it is to bolster it against reverse voltages, something that is bound to happen every now and then among their customers, it sounds a little less than professional... But hey, each unit broken this way may generate a new sale