If you are importing a text file into Word then there will need to be a 'translation' step whereby Word has to interpret the content of the text file. Do you get shown a dialog when you imported the text file which asked for the text format?

Yes I did. Does that make a difference>

Also, have you tried changing the typeface (font name) applied to the text. Does that make a difference to the comma characters?

So I just change the font, is that it?