Hello,

Just reviewing the spec and a handful of typos or minor style issues jumped out at me:

Abstract
--------
"...thus enabling better functional encapsulation within DOM."

-> "within the DOM"?


7 Styles
--------
"The flag signals that the rules, declared in an enclosing trees are applicable in the shadow DOM subtree."

Stray comma, or missing comma elsewhere? 
s/trees/tree/

"Even when the apply-authors-styles is set..."
-> "apply-authors-styles flag"?

"...produced using parent calculation algorithm."
-> "using the parent"?


10 HTML Elements and Their Shadow DOM Subtrees
----------------------------------------------

"If the element that can have fallback content, contains one insertion point."
I think some words might be missing from this sentence, it's confusing.

"The matching criteria value is universal selector..."
-> "the universal selector"?

"Otherwise, contains no insertion points or an insertion points that matches nothing."
-> second "insertion points" should just be "insertion point"

"All other <elements"
s/<elements/elements/

11.1 Extensions to Element Interface

------------------------------------

"1. If exists, discard current..."
If a value exists? Seems very terse.


11.2.2 ShadowRoot Methods
-------------------------

"2. Establish element, supplied as element argument as the..."
-> missing comma between argument and as?

"When invoked, it must return selection in shadow host's subtree."
Some determiners might be good here, -> "a selection", "the shadow".