The bug

Text formatting is not working correctly for right-to-left text in right-to-left languages. The position of the formatting character is reversed breaking the formatting. Additionally a "r" appears in front of the text which is likely used to reset the formatting but the formatting character for it appears to be placed incorrectly as well.

How to reproduce

1. Change your language to a right-to-left one, for example Arabic (first right-to-left language in language list)
2. Use the following command

   /tellraw @a ["",{"text":"في يوم من الأيام ، كان ","color":"gray"},{"text":"ناصر قيمر ","color":"dark_green","bold":true},{"text":"يلعب ماب باركور","color":"gray","bold":false}]