I don't think that there's a good answer to this. The following episode at least shows that people have been thinking about the problem of capitalizing Abelian for quite a while.
In her letter to Hasse dated Oct. 29, 1932, Emmy Noether informed Hasse that Ferdinand Springer had demanded that adjectives like "abelian" and "galois" had to be capitalized in all journals published by Springer. On Dec. 9, 1932, she wrote that she had passed on "Hasse's declaration of war" via Blumenthal (editor of the Math. Annalen) to Springer. Apparently Hasse had demanded that this should remain the author's decision.