As you enter your comments just don't click the "comment" button. Github saves the text anyway as you go. I don't know how long it takes to save the text (so maybe don't refresh or leave the instant you finish writing a comment) but in general they should all be there. Then you just have to scroll through and click comment on each one.

Certainly not as easy as seeing them in a nice row for review but it's a workaround at least.