at the end of the day whether things were added to the comic “on a whim” or not is totally irrelevant to how much meaning they have anyway. any piece added to the story, no matter what the intention with which it was added, serves to expand upon an existing piece. there is nothing in Homestuck that stands totally on its own with no connection to anything else. was it “necessary” for Jack English to be introduced for us to further understand Lord English’s process? no, but his presence still carries that additional information on his back, and is therefore not a meaningless detail.