I learned this from Gizmodo: Apparently if you select text in an email chain and THEN hit reply in Gmail, your email will only copy that selected text in the forwarded chain below your reply.

This is great news for when long email chains get replied to numerous times back and forth and you don’t really need the entire email message chain forwarded each time. This could save on mobile data too!

And best of all, this trick apparently works in most modern email programs too.