We have visited Greece in 2006, 2009, and 2011 and yes, we found this to be common. I believe the problem is the size of the pipes, not the toilets. The receptacle usually has a foot pedal so you don't have to touch it. Some of the newer hotels and museums do not have this system; you can flush your used paper. You get used to it. Odor isn't an issue most of the time as the receptacles are emptied frequently and have lids.

I have never run into this in Athens. But we did have an issue with it at our hotel in Santorini. I wish I could agree with TexasAggie that there was no odor, but we both noticed a funky kind of smell to the rooms on arrival, and it didn't disappear during our stay.

I have not seen that anywhere else either, but it is a habit in Greece, not only in hotels, restaurants cafes etc, but also in Greek homes.....

In public toilets you will see written : please do not throw papers in the toilet or in Greek : μην πετάτε χαρτιά στην λεκάνη

Personally i hate it, and never do it at home.... but you will be confronted with that everywhere in Greece....

On the islands and in remote areas many of the villages have old septic systems, not modern sewage treatment plants, and the systems aren't new. This means they can clog easily, so to keep problems to a minimum please comply and don't flush any paper products. Relax your expectations to adjust to this and you'll be fine.

I was surprised by this habit on my first trip to Greece but this is not a big deal. The request to to prohibit excess paper in waste pipes. It is especially critical in the islands. You can adjust to this minor requirement easily. The bathrooms are kept very clean and the receptacles emptied often. Enjoy your trip.

This is true in Cyprus too!

It's also common in South America.

I have run into this in many places around the world-some plumbing cannot handle the paper. No big deal!

Somewhere where we stayed in the Greek countryside had the same procedure as well as santorini.

I heard the owner of our hotel on santorini, in one of the rooms bellowing at a guest something along the lines of "yes, the notice does apply to your wife!" And then a long rant about Americans not being exempt and that a plumber would be needed. Is a bit gross, but not bad enough to spoil the beauty of the countryside and of the stunning caldera views. Maids emptied the bins often during our stay on santorini.

It takes about a day to get used to, and all good hotels empty the bin every day. All good guests comply with their host's wishes. If there is a smell in the bathroom it's not because of the bin, more likely a problem with the plumbing.

Seasoned travellers have encounter far worse in other parts of the world, e.g. the long drop toilets in Africa, or the jug of water that substitutes for toilet paper in India.

I would advise you to comply with this practice, it really isn't a big deal. It's definitely preferable to the alternative, (ignore the bin & flush it), the result can be awful, I have seen it! It was accomodation mainly used by Brits, a few of whom thought 'it doesn't apply to me'. They told other guests that it was ok, they were throwing the paper down the toilet, so more thought they'd do it too. It wasn't long before the blockage happened & sewage backed up everywhere. I won't describe the full horror, but suffice to say that putting a bit of paper in the bin then felt very pleasant compared to what they had just witnessed!
So, please, if there is a bin beside the toilet, use it

Multiply the mess Yiassas describes by all the toilets in all the hotels in a village and you can imagine what might happen if everyone disregarded the request to use the trash bins!

They have this on La Palma in the Canaries too. You soon get used to it.
Our last house on La Palma had super-duper loos with built in showers and dryers. Very flashy - took longer to get used to than loo paper in the bin did!

Is this question a matter of curiosity or is there some manner of problem involved?

It is clear from signs posted on most toilets that paper is not to be flushed. Why is this not the end of the matter?
Could bdj reveal their interest in the matter and why it has arisen please?

I know of one instance where an American woman was so uncomfortable with the idea of not flushing the paper that she made her husband search for a hotel that would allow it so she wouldn't have to "deal" with the indignity. Unfortunately he found one luxury hotel that was indifferent enough to the problem that they were allowing their guests to flush the paper, so they forfeited the money they'd already paid in advance for their room and moved to the hotel with no rule in place.

How silly. Not someone who should visit India or China.