[FabHK]

Very good question, and I haven't seen a definitive answer to it yet.

The responses by Bob are presumably numbered, and some might be delivery receipts, or contain delivery receipts (e.g. A cumulative ACK as in TCP). Could the server selectively suppress the read receipts, or manipulate the cumulative ACK? If it simultaneously triggered rekeying on Bob's side, presumably yes. But not seen a definitive statement on that.