4chan is actually an exception. While > on each newline is a standard for quote blocks in ASCII (and adopted by Markdown), 4chan’s “greentext” is rarely used to quote someone else. Ironic given that the frontend highlighting it is due to the quotation convention.

Also, there are some inconsistencies in the implementation. For example, Reddit will turn

> para1

> para2

into

para1

para2

but Lemmy requires the blank lines to start with > too or the paragraphs go in separate quote blocks. Also, Lemmy requires a space after the > symbol while 4chan doesn’t.