What is an example of a reasonable discrimination a state may exercise against a citizen of another state

For a long time, the United States was allowed to discriminate against women in combat roles. The argument was that combat roles needed to be men and so the government had a "compelling" interest.

This argument is going away.

it´s related to his charming character.

beauty is not everything, although we can joke that girls only care about the physical or material aspect, the truth is that a real woman looks at more important things, besides intelligence and personality, there are other attitudes that make irresistible to men who are 'unattractive'.

for example develop your sense of humor.