Lately I saw a young Muslim woman and a young Muslim boy sitting on a bench in a park. It seems they were flirting. Is this allowed since they met in a park where everybody could see them and they did not do any haram?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

If a young man sits (on a bench) with a non-Mahram young woman and they exchange courting words and the like, then there is no doubt that this is not permissible.

For more benefit, please refer to Fatwa 379204.

However, if the boy and the girl are married and they exchange courting words in a public park in front of people, then in principle this is permissible unless the words are obscene, or that this discussion leads to a disadvantage, such as causing temptation to others; in which case, this is not permissible.

Allah knows best.