Is it permissible to marry someone who stutters and involuntarily opens their mouth when speaking, and is that considered a defect?

Stuttering is not considered one of the defects that establish the option of فسخ (annulment) according to the majority of jurists. It is permissible to marry someone afflicted with it, and there is no obligation to disclose this defect. However, it is preferable to disclose it to prevent future disputes.