comma
We don't allow frame type extensibility any more.
negative -> positive
HEADERS can now contain padding; adjust PRIORITY flag language to suit.
Clarify when SETTINGS must be sent.
Combine two lonely paragraphs.
Remove extraneous sentence.
Consistently use SETTINGS to refer to the frame type, "parameters" to refer to more than one SETTINGS parameter, to avoid confusion.
Introduce the ACK flag a little more gently.
"both" makes it the tiniest bit smoother. Maybe.
extraneous "on"
Rework HTTP intro
clarify http mapping
explain E/C a bit more.
refine reason why 101 isn't right in HTTP/2
Align language in first example with later examples, and make it clear what's going on (it was confusing to refer to CONTINUATION frames when they weren't in the example).
Not a "sequence of HEADERS frames"
Revise HTTP Header Fields (and clean up from last one a bit)
specify what kind of request is being converted
Tweak header field ordering and give an example.