Users won't be able to make comments on the file as they only have read-only permission so that cannot edit the file.
As a workaround, you may try following:
1.Set "Restrict Editing" for that document and only allow for "Comment" of editing in the document.
You need to use Word desktop app to set restrict editing.
For details, please refer to Allow changes to parts of a protected document
2.Then share the document with users with Edit permission. Without knowing the password, users can't edit the content of the document, but they can add comment in it.
Note: protection enabled document cannot be edited in Word for the web, so users will need to open the document in Word desktop app to add comment.