By contrast, IGPs are *not* fundamentally rate-limited -- retransmissions are not congestion avoiding in any IGP that I know of. So, routing information heading into a congested link or router adds to congestion, which can lead to congestion collapse (and possibly consequent re-routing, moving the problem to another point).
Depends on what you mean by "fundamentally rate-limited". IS-IS is rate-limited to 30 LSPs per second per interface. As per ISO-10589. In IOS you can do some more configuration tricks. Recent IOS has improvements for rate-limiting in OSPF. Thank you Derek. EIGRP has probably the best rate-limiting of them all. EIGRP will never send more EIGRP traffic than a certain (configurable) percentage of the link bandwidth.
Finally, as a side-note, TCP also gives BGP the proper data-stream ordering and dramatically improves the odds that the receiving process will get exactly what was sent by the transmitting process across the network.
This can also be seen as a bug.
Many IGPs have really bad behaviours in the presence of lost frames/packets,
This depends. Are we talking hellos here, or LSAs/LSPs ? IMHO when a Linkstate protocol is deployed in a dense link network, a few lost LSAs/LSPs don't matter much. Henk.