This might be loosely related to an older question of mine.

I was answering a question at Mathoverflow and after posting I obtained a number of upvotes (in some sense signalling that everything was fine) until the OP complained about some “strange symbols” not rendering properly in his computer. It actually seemed OK on mine.

I edited the answer, nothing strange there until I copypasted the text onto Emacs and there I noticed some strange chars (labelled by a squared "OBJ"). So I corrected the post on my editor, pasted it and it was fine.

I do not remember doing anything strange while editing. I just checked and these chars are still there in the first version of the answer, source can be read here

Added. I'm using Chromium browser version 48.0.2564.82 Ubuntu 14.04 (64-bit) running on

Linux XXXXXX 3.13.0-77-generic #121-Ubuntu SMP Wed Jan 20 10:50:42 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

(output of uname -a). The only browser plugin installed and working is TeX for Gmail v.5.19.5.

  • 1
    Did you copy/paste your question from somewhere? – Patrick Hofman Feb 12 '16 at 12:59
  • @PatrickHofman No, I started from scratch in the editor – Pedro Sánchez Terraf Feb 12 '16 at 13:09
  • @PatrickHofman I recall copypasting within the editor, Linux style (select & middle click). Perhaps that's the problem. – Pedro Sánchez Terraf Feb 12 '16 at 13:11
  • 2
    It were multiple instances of U+FFFC, OBJECT REPLACEMENT CHARACTER. No idea where it came from, though. – chirlu Feb 12 '16 at 13:28
  • Do you have any plugins or antivirus or similar enabled, which may alter the textarea as seen in phabricator.wikimedia.org/T54327 ? – Nemo Feb 13 '16 at 9:53
  • @Nemo I updated the question with some tech info. Although I find a bit difficult to parse the webpage you link to, I think I do not have any such plugin. – Pedro Sánchez Terraf Feb 13 '16 at 14:13

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