You probably noticed that some authors of anagrams use pseudonyms. Most of them are members of the National Puzzlers League (NPL), an Americna non-profit organization focused on puzzling, primarily in the realm of word play and word games. Founded in 1883, NPL is the oldest puzzlers' organization in the world. it originally hosted semiannual conventions in February and September of each year, but conventions are now held annually, in July.
"National Puzzler's League,"
Word Ways: Vol. 44
, Article 34.
Available at: https://digitalcommons.butler.edu/wordways/vol44/iss3/34