This is an old question but it plagued me a lot recently until I found the answer.
Just add 'U0000FE0E' after the character that we want to prevent from becoming an emoji.
For example:
@"?" // should be written as:
@"?U0000FE0E"
Using the escaped unicode works as well:
@"u25B6" // should be written as:
@"u25B6U0000FE0E"
We need to use Unicode variants to prevent certain characters from becoming emoji.
Here is the article that solved my problem.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…