For code like this:

the ////////////////////// blocks are currently included by dsymbol as documentation:

If you look at http://dpldocs.info/experimental-docs/object.Throwable.html and https://dlang.org/phobos/object.html#.Throwable you will see that these block of comments are not included.
The ddoc spec doesn't mention anything about long /// blocks like this and also doesn't mention anything about the extra whitespaces between documentation declarations. It only says that ddoc comments apply to the next declaration if they only contain whitespace before. So I think ignoring blocks with only /////// lines would make this the easiest.
See Pure-D/code-d#307