The seat belt assembly is supposed to be under lifetime warranty from Honda. American Honda is trying to save money by making a distinction between the seat belt assembly's mechanical components (covered by warranty) and electrical components (not covered by warranty), even though the actual warranty (which I still have) doesn't make that distinction. In other words, it should all be covered for repair/replacement.

I filed a complaint with the National Highway Traffic Safety Administration
http://www-odi.nhtsa.dot.gov/ivoq/index.cfm
or call 1-888-327-4236,
The NHTSA representative told me that if enough people file a complaint about the seat belt warning system, the NHTSA will make American Honda recall the part(s) as defective. If you've already repaired the seat belt, you should still file a complaint, because you can get a reimbursement for the repair if there's a recall.

The NHTSA rep also told me that I should file a complaint against American Honda with the Federal Trade Commission (FTC) for Honda's failure to uphold their lifetime warranty on the seat belt assembly. I did that at:
https://www.FTCComplaintAssistant.gov/

To make your warranty complaint filing easier, here's American Honda's corporate info:
American Honda Motor Company
1919 Torrance Blvd, Torrance, CA 90501
phone: 800-999-1009