Edit: Do they allow buying individual bonds? I do that on Fido. Not a huge deal possibly.
Yes, they do (both US and globally)... limitation exists still on convertible bonds generally, so that is a problem.
On the upside, they allow you to place limits that are exposed on Bonddesk unlike FoK orders for bonds at Fido and all other retail brokers that I'm aware of. This exists at IB because their model isn't to profit by being a dealer in bonds, only on transaction volume / commish.
As said before, I think there probably should be two brokers - Fido (SCHW is good too) and IBKR. It's telling that everyone is arguing over those two, not whether the literally dozens of other mediocre brokers should exist. Lots of consolidation is going to happen in this industry.