Some possible mitigations from the top of my head (maybe ineffective): - warn prominently on hidden elements - randomize the number of enclosing div, on both

Some possible mitigations from the top of my head (maybe ineffective): - warn prominently on hidden elements - randomize the number of enclosing div, on both incoming and outgoing - compute what the forwarded message would look like on forwarding, ask for confirmation if differs significantly. Or do the opposite (probably more effective since doesn't require other clients to help)