"that all clients will start"

Only need one closing double quotation mark.

"each"

dele

Written elsewhere as "timed text format". Should be consistent.

"is"

Need type per spec?

No "@"

As an implementation note, I think we are wanting to push a little harder for our preferred case, but certainly without excluding or shaming ppl who have their reasons for doing it a different way.

Implementation Note: Using Thumbnails