Why Overlay should be disabled by default in all Drupal 7 profiles

After discussing the d7ux overlay accessibility issue with several at Drupalcon, and mentioning the issue in my lightning talk at the Core Developer Summit I noticed that an Allow users to opt-out of the overlay issue had been opened in the bug tracker. Overlay is a contentious topic for some in our community, and I will not rehash all of the pros and cons for Overlay's inclusion in core. I will however attempt to concisely present an argument for Overlay being disabled in all Drupal 7 core installation profiles.

1. Drupal is an inclusive community; we are building a tool to be used by everyone; nobody should be excluded (if at all possible).

2. Overlay, based on the jQuery UI Modal Dialog, cannot be made to work for all users. You can read my explanation of this by reading Can a modal dialog be made to work properly for screen-reader users on the web?. You may also be interested in reading through the jQuery Accessibility mailing list topic on dialog accessibility. In summary, it is not jQuery's implementation of modal dialog, but the fact that not all assistive technologies can currently properly interact with a modal dialog on the web that causes the problem.

3. Since we are enabling, by default, a module that will cause significant problems for some unsuspecting new users, then we are not being a responsible inclusive community.

Pros of disabling Overlay in all Drupal 7 installation profiles:

1. No unsuspecting user will be confronted by an overlay that they cannot use.

2. When site admins go to enable the overlay module we can provide them information about the accessibility limitations of the module, allowing them to make the best choice for their user base, meaning less users are excluded.

Important note:

I wish that overlay was not a problem. I wish that modal dialogs on the web were accessible to all users, so that this problem would not exist. But, this is not the case. Our community finds itself in a difficult place, and we need to make a difficult decision. Do we continue to show the world that we are an inclusive community, building an inclusive tool that can be used to grow inclusive communities, or do we choose to make choices that are counter to our community's cultural values and to exclude what is arguably a small subset of members for sake of convenience. We must decide as a community which direction we will go.