ISP problem fixed
It took longer than it should have (roughly two weeks), but in the end the problem I was having accessing Akamai hosted websites such as eBay Canada, Chapters-Indigo was resolved.
I had to use the BroadBandReport web forums about Cogeco, to report the problem to some dedicated Cogeco employees who eventually took a closer look at my problem (the traceroute ICMP checksum errors appear to have been a red herring), and in the end they found both a broken Akamai box, and a bug-like issue (I think means a misconfiguration or an obscure error).
So the problem was fixed, and I can buy obscure computing and RF gadgets at surplus or near-surplus prices again, and appease my bibliophile tendencies.