@Michael that is very helpful. Just one additional detail might be useful. You got the model number MY2H2FD/A which is actually the Apple stock code which also identifies things like color. If you tap on the MY2H2FD/A code it will change to a model number like A1234.
With that extra detail it sounds like there is probably enough for anyone who can demonstrate the problem to submit a Bug Report direct to Apple using the official Feedback pages. I don’t think there is a major need to juggle iso and ansi layouts if the fault is demonstrated.
Product Feedback - Apple
The ideal format for a bug report would include something like:
Details of the hardware and software, example, iPad 12.9 4th Gen model A####, iPadOS 26.0.
Short steps to follow to demonstrate the bug (basically as you tried, mention the selected keyboard language and AZERTY layout)
Observed result including which app you tried typing to see the double width commas
Expected result.
If you are able to include a link to mention this thread it would probably help, if the feedback page will allow it.