My last bug report on this list was prepared with org-submit-bug-report in an Emacs with a minimal configuration. From there I copy/pasted the contents of the resulting mail buffer to an mu4e mail buffer in my fully configured usual Emacs. Then I finished the bug report and hit send.
mu4e noticed non-printable characters in the mail and asked what to do about it. The mail contained e.g. something like ("ftp" :follow #[257 "\301\300\302^CQ!\207" ["ftp" browse-url ":"] 5 "\n\n(fn URL)"]) where ^C was not ^ followed by C, but the way Emacs dispays some particular non-printing character. I told mu4e to replace the characters. Apparently, all non-printable characters have been replaced by ASCII periods. Is there a best practice? Leave or replace?