What's the connection between block space and fidelity bonds? I understand that fidelity bonds serve a purpose by discouraging attackers from launching sybil attacks, as they would need to lock up bitcoins for an extended period.
In JoinMarket and Whirlpool, one participant pays for the other participant's block space. This creates a misaligned incentive that encourages a single person to assume many identities in order to be chosen for this free handout as often as possible. This misaligned incentive is corrected by fidelity bonds in JoinMarket which allow the free handouts to be targeted towards distinct participants.
Since there are no free handouts in WabiSabi, there's no job for fidelity bonds to accomplish.
Can you quote your specific message instead? There's a lot of discussion there.
I did quote the specific message, I'll just copy and paste the content here:
A malicious coordinator may tag users by providing them with different issuer parameters. When registering inputs a proof of ownership must be provided. If signatures are used, by covering the issuer parameters and a unique round identifier these proofs allow other participants to verify that everyone was given the same parameters.
As noted, you can register multiple inputs with WabiSabi to verify that the parameters match each other.
A malicious coordinator could also delay the processing of requests in order to learn more through timing and ordering leaks. In the worst case, the coordinator can attempt to linearize all requests by delaying individual to recover the full set of labelled edges. This is possible when k = 1 and users have minimal dependencies between their requests and tolerate arbitrary timeouts but issue requests in a timely manner.
As noted, clients would be able to detect this and defeat it by disallowing arbitrary timeouts.