If you reply to an encrypted email which is in PGP/Inline format then the new message does not contain the shown cleartext as quote but the PGP/Inline encrypted data. There is an "easy" workaround (but you have to know the possibility; thus I have not marked this bug as minor): If you mark the cleartext before replying then the cleartext is quoted. Reproducible: Always
Can you please verify that the bug is still there under 4.10.3? *** This bug has been marked as a duplicate of bug 298911 ***