With standard quotes, you can use advanced formatting, such as paragraphs.
> Sentence 1. > > Sentence 2.
However, this is impossible with spoiler blockquotes.
>! Sentence 1. >! >! Sentence 2.
Sentence 1. Sentence 2.
I think the spoilers should behave the save way as standard block quotes. Sometimes, it's nice to put a big explanation of the code in a spoiler, and currently I'm forced to use ugly
The issue is most likely caused by that spoiler block quotes are a hack, involving checking if the block quote begins with
! after rendering Markdown. This should be a part of Stack Exchange Markdown implementation in my opinion, not something implemented over actual Markdown.