Have a checklist of things to consider for each change

[zcorpan]

In #1937 (comment) @therealglazou says

first, I think this should NOT have been merged in issue #1945 without some metrics on impacted Wysiwyg editors...

We should do better in the future.

Maybe we can have a checklist of things we need to consider for future changes to HTML, so we remember to consider impact of editors, learnability, accessibility, and so on.

[therealglazou]

I think it's a VERY good idea. As I said in the reference issue, any change in the content model has impact, for Wysiwyg content editors, on CR behaviour, copy/paste, transformations of an element into another one, and more. Some model changes that seem light could be really tricky to implement. As an example, the U/OL model: when it was originally designed, nested lists were considered as siblings of list items, and rejected. The final model made more sense but was so painful to implement it took Dreamweaver years to implement it (with some caveats) and Gecko still does not manage it correctly.