indent_string not working in 1.5.16 and 1.5.17

[Randall Hopper <viznut@xxxxxxxxxxx>]

Hi all,

Long time mutt user.  Recent distro upgrade bumped me to Mutt 1.5.16, and
in this version, I can't get "indent_string" to work at all.

In Mutt, I confirm:

  indent_string=" |"
  text_flowed is unset

But no indent string is applied to most messages at all, and only the
standard ">" for replies to flowed messages.

I've RTFMed, and even updated to Mutt 1.5.17, with no success.  What am I
doing wrong?

Thanks,

Randall