A French nonprofit said it was considering making complaints against some Twitter users following an explosion of French-language anti-Semitic messages. SOS Racisme, a Paris-based anti-discrimination organization, made the statement on its website after the phrase UnBonJuif on Oct. 10 became the third most popular hashtag among French Twitter users. Literally meaning “a good Jew,” it served thousands of Twitter users to enter what the French daily Le Monde termed “a competition of anti-Semitic jokes.” One Twitter account registered to the username “Marcel Leblanc” posted a picture of an emaciated Jewish woman taken in a Nazi concentration camp as his or...