According to some versions of Mahabharat, especially Gita Press translation, it is mentioned that when Karna came forward to fulfill the condition of Draupadi’s swayamvar, she stopped him just before he could fire the shot saying, “I will not marry a Suta.” 

Some people quote this incident as justification behind Karna’s hatred towards Draupadi.

I personally don’t see any problem with the fact that Draupadi refused to marry Karna, since it was her Swayamvar and she had all the right to choose whom she wanted to marry. 

Having said that, this particular shloka is not present in Southern recension and even the researchers at Bhandarkar Institute also have concluded that this refusal did not happen, instead according to Southern recension and BORI CE, Karna did make the attempt to fire the shot but failed, hence there was no situation where Draupadi had to refuse Karna. 

This version makes a lot more sense than the northern recension, considering when Dhrishtadyuma introduced all the attendees, he never made any special mention regarding Karna or him being a Suta. Even in Gita Press edition following Shloka in next chapter confirms that Karna failed to fulfill the condition of Swayamvar, thus strengthening the case against “सूतम् न वरयामि” narrative.