reiyasona said:
Quick / temp fix: Click on your HTTPS Everywhere symbol while being on the pixiv.net domain and deactivate the "pixiv (partial)" rule (written in green letters).
This may prevent the issue from occurring in posts one uploads or commentary one pastes in after following the above steps. However, I followed the directions, then opened an existing commentary, and the "�" symbols were still generated. I tried logging out and then back in to Danbooru with HTTPS Everywhere now active, and got the same results.