Do you send a compiled .html file for your friend to run directly in their Firefox installation, or do you send the raw .txt files for your friend to render through their own ChoiceScript installation, or do they test your work through Dashingdon?
I ask because multireplace is a fairly new feature! It was added in May of this year. That’s 2017 if anyone in the distant future is returning to this topic.
If your friend is using an earlier ChoiceScript installation to render your .txt files, the multireplace option will never work for them. As a dedicated Firefox user myself, I’ve never experienced any trouble with multireplace that wasn’t entirely due to my own typos and errors.
However, if they’re testing your work through Dashingdon (or you’ve sent them a compiled .html file that functioned correctly on your own computer) the age of their ChoiceScript installation shouldn’t be a concern.
Now, it’s possible I’ve misunderstood the situation, and your friend is testing their own work rather than testing yours. In that case, Dashingdon should still render multireplace in their .txt files correctly. However, both compiling their own .html file and running the .txt files raw will produce the same result, which will depend on the age of their ChoiceScript installation. As I understand it, Dashingdon allows authors to upload either .txt files or .html files. It then renders .txt files with an up-to-date ChoiceScript installation, but does not update compiled .html files.