It would have to be false in order to be libelous.
You'd think so, wouldn't you. If only. I'm not sure about Polish law, but if it's anything like English law, it doesn't have to be false to be libelous. The important thing is
how it's written, the intention in writing and (most importantly) how it's taken by whoever is assumed to read it and the effects which result from that.
If it's about rip-offs, I have a good story, recent too.
I rented a flat for five years. On moving in, all meters were read, the amounts recorded and everything was signed.
It puzzled me that there were only two water meters, one for the kitchen and one for the smaller of the two bathrooms. But the owner of the flat was on the management board of the spoldzenia (housing co-op), and very much one of the great and the good (a reasonably well-known person here, important enough to have an official car and driver), so I assumed it was either in order or not a potential problem. There were other irregularities too, but I assumed she knew what she was doing. After almost five years, some people from the spoldzenia visited, opened some fitted furniture in the bathroom and took it off the wall with a crowbar. I told them they should speak to the owner, a director of the spoldzenia, but they told me she'd been voted off the board, and the chickens were coming home to roost.
They revealed a water meter, boxed in behind a very firmly fitted permanent cupboard, covered in twenty years' worth of dust and cobwebs...
Apparently it had never been read. Ever. Even though she and her (large) family had lived there for ten years and the flat had been rented out for another ten.
The owner later turned up with an absolutely huge bill (five figures) and said I must pay it, because it's in the contract.
Fortunately for me the rental contract had expired three years before, but she still made all sorts of threats about legal action, debt registers etc. Nice about it, but very firm that the money must be paid. She brought an English-speaking relative, even though she knew very well that I'm fluent in Polish. Though this was all just bluster.
She doesn't have a leg to stand on and won't get so much as a groszy from me (and frankly doesn't need it), but I can imagine some people taking fright and paying at least part of the bill.
Obviously I left, and quite reasonably withheld the last month's rent and utilities money to compensate me for the hassle of having to move at short notice, having the spoldzenie breaking the cupboard from the wall with a crowbar (while I had dinner guests), and being threatened with a bill for ten years of her family's and five years of the previous tenants' water bill. But I can just imagine it happening all over again to someone who would just worry and pay something..