Another speciality of Calamus: You can write the selected text from right to left. This has nothing to do with mirror images; rather, the characters are added from right to left, instead of from left to right. You may turn this feature on or off by clicking on the icon. Due to kerning of the characters, a text written from right to left can have a different width compared to being written left to right:
This function even allows you to switch the writing direction within a line.