You're not the only one. My interest was piqued by reading Simone Weil who was an admirer of Catharism and although they are described as dualists, wikipedia writes:
The idea of two gods or deistic principles, one good and the other evil, was central to Cathar beliefs. This was antithetical to the monotheistic Catholic Church, whose fundamental principle was that there was only one God, who created all things visible and invisible. Cathars believed that the good God was the God of the New Testament, creator of the spiritual realm. Whereas the evil God was the God of the Old Testament, creator of the physical world whom many Cathars identified as Satan.
This doesn't seem particularly controversial to me; and besides, given how few of their texts have survived (given the violent suppression by the then Catholic Church), it can't be taken as read as the whole story; in fact, Simone Weil regarded the great failing of Christianity as its embrace of Rome; in her mind, the epitome of maleficent power, if not the original Babylon, it's avatar; this is one reason, by her own admission why she admired Catharism.
This is why Thibon took the trouble to defend her against this charge:
A great deal has been said about her Catharism; a letter from her, said to have been written in 1940, was brought to light in 1947. In it she spoke of her admiration for the Catharist movement and used the word adherence as opposed to curiosity ... If this letter really was written in 1940, I should say that in 1942 she had greatly changed and had no longer any traces of this attitude about her except her love of the twelfth century, where Romanesque architecture, the troubadours and the language and civilization of
Provence (the Pays d’Oc) all shared her admiration of the Cathars.
She was a Marxist when Marxism was in vogue but not doctrinally so - it stemmed from her deep sense of compassion - not something that most Marxists at that time were known for according to at least one writer on her work; in fact, she often was contemptuous about small-minded Marxists who hadn't taken even the trouble to understand what a dialectic was, or even cared; nevertheless, she outgrew this phase quite early on but remained a revolutionary thinker who also happened to disagree with Trotsky...like many complex thinkers their thought defies easy categorisations.