Test passes if the two boxes below look exactly the same.

Key to entities used below: ‎ - LRM, the invisible left-to-right mark (strongly LTR). ‏ - RLM, the invisible right-to-left mark (strongly RTL). We use text-align:left because neither the dir="auto" nor the unicode-bidi:plaintext specification states whether text-align:start and text-align:end should obey the paragraph direction or the direction property in a unicode-bidi:plaintext element. 
@‎123‏!
!‏123‎@
@123‎‏!
!123‏‎@
        
@‎123‏!
!‏123‎@
@123‎‏!
!123‏‎@
        
@123!
@123!
@123!
@123!
        
@123!
@123!
@123!
@123!