I only just checked my feedback and noticed a comment: "The postage paid by the other user was insufficient. Comment: 2.20 in cost due to lack of postage" 

Now I thought the RM charged you £1 to pick up items with insufficient postage plus the extra postage missing, if this were the case then the insufficient postage would be £1.20, but I send out a very small thin book (with correct postage as far as I was aware), and the postage rates are...

 Large letter

So how on earth can the other users comments be correct? Also why didn't they email me about the problem? I always get a proof of postage so would have the receipt to prove I sent the book and could have put in a claim to the RM for them.

I'm a bit disappointed & upset about this as they also gave me a 3 star rating.  :(

 Is it possible they left me feedback that was meant for someone else? Is it worth trying to do anything about it?

I agree with what you've said, doesn't seem to tally with the amounts due for postage, even assuming that the postage you did put on it fell off. Might be worth emailing the other person to apologise but query it. Sounds like Royal Mail may be at fault, or else underpaid postage charges have gone up too!! Would be interested to find out the end result.

(And of course, if you have a proof of posting you should be able to get the "fine" refunded!)

I would definitely email the other swapper to apologise, but explain as you've explained here that you're a bit confused by the excess charges.  If they can explain it satisfactorily, then you could offer some form of compensation (eg stamps or another book off your list) which might persuade them to up your rating.  Otherwise, I guess you just have to accept it and move on.  It won't take long to disappear down your feedback page.

It sounds like the other swapper has made a mistake ....I had to pay excess, a while ago now, but it was £1.00 handlling fee and the excess was only a few pence...