This is so true! The buyers will nag and abuse sellers in comments.
When I have the offer button enabled, it is amazing how often I will have the same buyer repeatedly submit very low offers until the offer limit is expired...then seconds later they will start on the next cycle of low offers! I had one buyer do this for 6 cycles in a row nonstop until I realized that I could not respond to his offer and that would delay his ability to make more offers! I wanted to keep the offer option intact on that item because I was getting good offers from other people, but it was so annoying. I have my notifications set to email, text and phone banner so I don't miss an offer/comment/purchase, but it makes it so annoying to go through the offer process with a time wasting non-buyer.
The only way I have found to stop this type of buyer is to not respond at all to their offer (once they have demonstrated that they are unaffected by my counteroffers). If I decline they can keep offering, if I counteroffer they can keep offering, but if I ignore them then they cannot offer for at least 24 hours.
I had a buyer last night who offered me $2000 for an item that I had listed for $2850 (about $2K for me after commission) and goes for about $4000 on most resale sites like ebay. I countered her once with $50 off and she declined/responded with the same offer. After going through the whole 3 offer process with her where she never increased her offer I just disabled the offer option on that item and went to sleep. I woke up this morning to a rude comment from her, "They are available all over the world, please reduce your price."