I am not aware of any restriction imposed by govt of India on the operation of any commercial flight between India & China. Airlines are free to take the decision based on their own assessment on ground.
E-visa is available for certain categories of visits to India; Diplomats don’t fall in that category. A diplomat visa is applied at the embassy. So, it may not impact the diplomatic process.
Coronavirus: All existing e-visas from China are no longer valid. Similarly, normal visas that have been issued are also no more valid. Those who have compelling reasons to visit India, they can contact our embassy or the nearest consulates to apply for visa.