Thank you ETFbitcoin for the link, I read the full article and it only proves my point so I guess you misunderstood my previous reply.
What I was trying to say is that a customer will gain nothing by performing a malleability attack because, in our case, he is making a deposit. All it can cause is some nuisance to the customer service.
The attack can cause monetary loss in case we were talking about withdrawal transaction IDs. In such case if the service monitors only the txids then the attacker can claim he didn't receive his money and asks for a refund (it can be more dangerous if the refund process was automated).
I hope you got my point.

However, I agree with all the comments above. This is the worst approach when it comes to monitoring transactions.