bidi-string-mark-left-to-right is a compiled Lisp function in `
Return a string that can be safely inserted in left-to-right text.
Normally, inserting a string with right-to-left (RTL) script into
a buffer may cause some subsequent text to be displayed as part
of the RTL segment (usually this affects punctuation characters).
This function returns a string which displays as STR but forces
subsequent text to be displayed as left-to-right.
If STR contains any RTL character, this function returns a string
consisting of STR followed by an invisible left-to-right mark
(LRM) character. Otherwise, it returns STR.