Why are the comments disabled by default on my custom_post_types?

Ok – so I solved this. Here is what appears to be the problem.

Comments are disabled by default for custom-post-types. This happens even if
you have them enabled in the overall settings

To fix it, all I had to do was the following:

1. In SETTINGS > DISCUSSION uncheck the “Allow people to post comments on new articles” setting.
2. Click “Save Changes”
3. Now go back and re-check “Allow people to post comments on new articles”
4. Click “Save Changes”

It seems that for custom post types you need to kind of kick-start this setting. All new posts for created custom-post-types will have the box enabled by default. Existing posts will retain their previous setting. I’m assuming it’s the same for allowing trackbacks. Hopefully this helps someone…