It came up in discussion at #2556379: Map does'nt display on node edit form → that it would be a good idea for the #attributes documentation in the form API reference to be a little more specific about when it shouldn't be used, for example by mentioning #id as a case where you'd usually prefer to use the main form API property to set the attribute instead.
Closed: won't fix
API documentation files
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Thanks for working to improve Drupal.
This is for the Drupal 7 Form API reference. Since Drupal 7 is past end-of-life this is now a "won't fix".
Work on documentation for form elements for supported versions of Drupal is at 📌 [meta] Move/Create Form Element Documentation Active and 🌱 [Meta] Improve documentation for Render and Form Elements Active .