What does "if vexed" mean in this context below?

He approaced English linguistic and literary conventions aslant, but the seeming handicap of his foreignness helped him bring to the English novel a fresh geopolitical understanding, a formal seiousness, and a psychological depth, all of which opened up new possibillities for imaginative literature in Enslish, as indicated by his profound, if vexed, influence on later writers as different from himself as the Nigerian Chinua Achebe and the Anglo-Trinidadian V.S. Naipaul.