Max, the idea in your link led to another, which may be particularly helpful when writing a post that need special characters often, not just once or twice.

Some word processors have quick access to these characters. (In Microsoft Word you can reach them by clicking the Edit tab, and then subtab Symbols".) To take advantage of that access, one can simply use the word processor to write the post, and then paste the post onto the board.

BTW: I couldn't find the schma symbol.