Well, the function of anti-trust law is specifically to target massive unchecked power.

If you're the supplier with a Shopify and Amazon Merchant account, or a local grocery store with white label products, none of this applies to you because you don't have the capability to effectively hold other businesses or markets hostage, no matter how aggressive you are.

No, that's not what a platform is. You can always sell your product direct to consumer. You just can't be the intermediary for both your own and other companies' products on the same site.

Alright, so you actually can be a manufacturer and a retailer at the same time, just with your own products on a separate website.

Are manufacturers legally barred from linking to the marketplaces of its peers?

Could Amazon not just maintain two websites, and shut down the marketplace for certain goods when it feels it has enough information to sell its own versions on the other site?

If not, could Amazon not just sell the information it would have used to develop its own products to another company (which we'll assume is totally unrelated) to develop its own off-brand products, and then treat those products preferentially?

I think those are good implementation concerns. Maintaining two separate websites isn't really an option under the supposed regulation, that's still one company being a platform and a manufacturer. The second option seems alot more likely to be allowed -- but now, at least you've created a market for that information and it's not just Amazon that has access to the data. Not sure I understand why it would treat the those products preferentially though -- unless you're bundling selling that information with product placement fees, which doesn't seem to be related (or necessary). I would assume product placement would be another revenue stream for the platform, like it is now for brick and mortar retailers like walmart

The software corollary would be that Apple can no longer host GarageBand and Keynote on the App Store, and Google can no longer host GMail or Google Docs on the Play Store.

I think that's a great call-out. It's interesting that we don't see the same problem in app stores -- probably because there's not much profit motive for apps like there is for general retail.

If they are different entities, how come Amazon Basics can use the same name as the platform? Did Amazon sell the rights to another company to use their brand?

"Did Amazon sell the rights to another company to use their brand?" But of course, why not? These kinds of trademark licensing agreements are all over the place, there would be no difference here.

Then I'm not sure why it's a problem. Ostensibly anyone could have bid to license that name; I see no issue with that.