have to say I would like to be able to quote(partially or full) (what you name “advanced message forwarding”)
I think it is an useful feature. +1
About the stickers: since email have a cost to me, I would prefer stickers themes like in Pidgin where a text like :sticker-name: is sent and the app replace it for the proper sticker, this “:sticker-name:” could be sent as a link to the actual sticker hosted somewhere so users not using Delta Chat can see it, and it stay compatible with other MUA.