In following paper, written by Christian Decker et al., there is a paragraph that is not clear to me.
"The central idea of Lightning is to invalidate an old state by punishing the participant publishing it, and claiming all the funds in the channel. This however introduces an intrinsic asymmetry in the information tracked by each participant. The replaced states turn into toxic information as soon as they are replaced, and leaking that information may result in funds being stolen. The asymmetry also limits Lightning to two participants."
There are following points that are not clear to me:
(1) Does asymmetry mean the information tracked by each participant (payer and recipient) are NOT the same (or are NOT equal)?
(2) What is the reason of this asymmetry?
(3) What does "turn into toxic information" mean?
(4) The last sentence: "asymmetry also limits Lightning to two participants", Does it mean that we can expect a payment transaction can have more than two participants? since a payment logically has only two participants: a payer and a recipient.