Which bidding system is assumed by default at Bridge Base Online (for humans)?
I asked in chat several times in different games (ten times I think) and nobody answered.
Simple answer- No system- its an open community. If high level players like JEC don't need to specify a system why would anyone else. Partial answer- Most English speaking bridge players are American so can assume they play some sort of Standard American- they assume you are psychic so you know what they play.