Hey Zofia,
I'm not sure what you're trying to do exactly, but there might be a couple work-arounds. While they aren't as specific as commenting, they may work for you.
One is for the user to "print as PDF" the form. They can re-open it and use the comments editing tools, however the form will at that point be static. I'm not sure if this makes a huge difference for you, but it's worth a shot.
The second is to add a field or fields for comments at specific places in the form. This would probably work if you know in advance where and what types of comments you expect. You can either display the field upon clicking a button (add comments) or just show it automatically. I'd lean on allowing the user to select to view the comments field.
Of course, in order to have the data saved, users that enter data must either have Acobat Pro or you must have Reader Extensions in your enterprise.
I know we struggled with the "inability to make comments" until we thought of it a different way. Now we actually added several comments fields into our XSD and capture it. As long as your file is well-planned, your users probably won't even miss using the tools.
I hope that helps a little.
Thanks,
Lisa
