Marking included text in replies

[bernie]

I've had to reinstall Aqua mail on my tablet {I *still* haven't managed to get the ?@#!@#$% google play payment to work}  and I've noticed that when I do a "reply" the previous text seems to be marked with vertical bars {|}.  I'm old school and in my previous setup I got it to demark the replied-to text with old school ">"s.    I've looked through everything and I can't figure out where that's set.

[bernie]

Well, I've sort of figured it out.   I found, in Composing and Sending "Prefix for plain text replies"... grayed out [as is "Quote the original" which is checked but grayed].  Why/how would they be grayed?  and of course: how do I ungray them