[mike rugnetta voice] here's an idea: the twitter thread is the new greentext.
but i think they are similar in that they both stem from features/limitations of the platform (namely the formatting of 4chan posts and the character limit of twitter posts), and they both serve to express ideas that are difficult to express in the default posting mode
@0x3F oooh yeah good point
@lycaon 4chans greentext also took into account context when used in a response, >implying being a common example of this.
I think the usage of these tools is more than just a combination of limitations of the platform, perhaps a product of the culture involved in each of those websites, as well as the versatility in each of the tools. Twitter threads can't really be used for anything but saying *more* (afaik), but ">" by itself has little meaning on its own.