I think the definition in (the new) 2.3 of wrapped and unwrapped is still a bit imprecise and self-referencing, but I think the fix is simple.
I would suggest adding the words "defined by this specification" at the end of the second sentence, giving:

"Use of wrapped format indicates that notification messages should be contained in a wrapper element defined by this specification."

Without such a qualification this would lead to ambiguity as one person's wrapper is another person's unwrapped!

And just being pedantic I would also suggest changing:

"Use of unwrapped format indicates that notification messages are not wrapped."

To

"Use of unwrapped format indicates that notification messages are not contained in a wrapper element."

I also think the second paragraph is confusing, as formatting is always engaged, it's just a question of what sort!

So how about changing:
"When the Delivery Format feature is engaged the formatting of the going events occurs after any filtering."

To:

"Filtering occurs prior to any formatting of notification messages." 

The sum total of these suggestions would give:

"2.3 Notification Formats

This specification specifies two delivery formats: wrapped and unwrapped. Use of wrapped format indicates that notification messages should be contained in a wrapper element defined by this specification. Use of unwrapped format indicates that notification messages are not contained in a wrapper element. 

Filtering occurs prior to any formatting of notification messages. This ensures that regardless of what type of formatting might occur, the same Filter dialect/expression can be used to subset the event stream."