I often use singular they to keep my sentences gender neutral. Many of my friends (none of them are native speakers), however, consider this to be grammatically incorrect, and suggest me not to use it in formal English exams.
My questions are:
- Is singular they widely accepted in English speaking countries such as America and Britain?
- Is it formal enough to be used in formal situations, such as a public speech?
- Is it casual enough to be used in informal situations, such as gossiping among friends?