Version:           4.8 (using Devel) 
OS:                Linux

With the new "Reply using HTML" feature turned on, default (or custom) templates are severely deformed both for replies and inline-forwards.

E.g. with the following reply template:
  On %ODATE %OTIMELONG %OFROMNAME wrote:
  %QUOTE
  %CURSOR
only the filled placeholders %ODATE %OTIMELONG %OFROMNAME are displayed, while "On", the spaces and "wrote:" is missing.
Also, the Cursor is not set to the requested position.

Another example: With the following a inline-forward template:
  ----------  Forwarded Message  ----------
  
  Subject: %OFULLSUBJECT
  Date: %ODATE, %OTIMELONG
  From: %OFROMADDR
  %OADDRESSEESADDR
  
  %TEXT
  -----------------------------------------
all header field names are stripped off (except for "To:", "Cc:" etc. which is provided via the placeholder.

Reproducible: Always

Steps to Reproduce:
1. Turn on "Reply using HTML if present".
2. Select a HTML message
3. Hit "Reply" or "Forward inline"

Actual Results:  
just the substituted placeholders

Expected Results:  
the full template with the placeholders being substituted