CSF Rhinorrhea: This condition involves the leakage of cerebrospinal fluid (CSF) through the nose. The clear, thin liquid and its occurrence when bending forward suggest a possible connection between the cranial cavity and the nasal passages, which could be due to a defect or injury. The absence of salt or metallic taste and other symptoms like seizures or neck pain does not rule out this condition, as the presentation can vary.

Allergic Rhinitis: Although the description does not perfectly match typical allergic rhinitis symptoms, it's possible that the clear discharge could be a manifestation of allergies, especially if the discharge is watery and occurs in response to specific allergens or positions.
Vasomotor Rhinitis: This condition involves an overactive nasal response, leading to excessive watery discharge. It could potentially cause clear, thin liquid to come out of the nose, especially when bending forward due to increased nasal blood flow and pressure.

Skull Base Fracture: Although less likely given the absence of trauma history or other symptoms like seizures or severe headache, a skull base fracture could lead to CSF leakage. Missing this diagnosis could have severe consequences, including meningitis.
Encephalocele: A rare condition where brain tissue protrudes through an opening in the skull, which could potentially cause CSF leakage. Early diagnosis is crucial to prevent complications.

Cerebral Spinal Fluid Leak Due to Tumor or Cyst: Rarely, tumors or cysts in the skull base can erode the bone and cause a CSF leak. The presentation might be similar to what is described, with clear liquid coming out of the nose, especially with changes in position.
Nasal CSF Fistula: A fistula or abnormal connection between the nasal cavity and the cranial cavity can cause CSF to leak into the nose. This could be due to congenital defects, trauma, or surgical complications.