I didn't aware of this seize of Chipmixer until I stumble on this thread so thanks OP for this thread
Welcome

Maybe because the information that will be presented is not useful? The forum collects basic information such as IP addresses and other simple data that does not lead to a general failure to reveal identity, so I do not think that they are looking for such information, but they always go to email service providers, Apple and Google.
More data they will get from members like @DarkStar_ or at least they may try to get it.
Strangely enough, no data was reported from Proton's email, although it was the main email that the team used.
They have already published their case against the owner/operator of Chipmixer therefore they probably will not be seeking to get any more information to strengthen their case against him.
I hope that settles that then. Others in the forum have quoted the same section of that law, I hope that settles the concerns.
As for paying back, there have been other mixers seized and nothing happened to the people wearing those sigs.
There have been scam ICO / IEO and everything else shut down by authorities and nothing happened to the people wearing those sigs.
There have been cases of casinos shut down by authorities and nothing happened to the people wearing those sigs.
And so on.
You are right those casinos and ICO/STO/IEO scams that made anonymous people behind them overnight multi-millionaires, how many of them were ever brought to appear in Courts to face justice?
If the general consensus in the forum is one of calm for those that participated in the signature campaign then that is precisely what is needed at this time. You are right, there has never been a case of any authorities asking signature campaign participants to repay monies. I hope the authorities do not start trying to do it now as a deterrent to stop people promoting mixers.