It can be done quickly:
- If you use Chrome you can resize the text field. Set it to a width that seems just right for where you want to insert line breaks.
- Insert the initial " > " (I put a ">" in front of each line but that's just me), select it, copy it.
- Now just using keys END, DOWN-ARROW, RETURN, CTRL-V insert all necessary line-breaks. Setting the text field width causes the END key to go to exactly the right position automatically, no need to navigate the words manually. then RETURN and CTRL-V to insert the line-break and the quote-start. Repeat.
This way you can manually format even long quotes very quickly.
Don't overload monospace formatting for block quotes. It is bad at them because they are not what it is for. Just quote with a leading > and let the user agent reflow text as it needs to. Everyone will know what you mean.
I don't add the following links because that's where I got my opinion from, it's only in support. I came to my own opinion by reading a lot on the web :-)
In addition, only very few people in this forum use that method for large quotes, so without consulting a style guide, it seems to me most people feel that way.
https://answers.yahoo.com/question/index?qid=20100502220045A...
http://grammar.yourdictionary.com/punctuation/when/when-to-i...