I think that the rehash of the Sue-Cliff affair was almost daytime-worthy. They could have done better things. Dusty was axed too soon, and Sue right away was falling under JR´s spell (she was feeling pity of him when Jock died already!). The most interesting thing of all this was how the other characters interacted with them in those episodes. Rebecca, Ellie, Afton, Clayton, even Katherine. Funny how Rebecca never saw Sue until Cliff was in the hospital.
Rebecca (Off): "Take that awful woman out of here!
She´s a tramp, a drunk and an unfit mother...
just what I used to be..."
Afton evolved by then when she seemed to realized that she didn´t only "want his money" but also the rest of him. By the writers´ choice or not, that was a pivotal moment for her, when she started to be more warm and loving towards Cliff and also Pam and Mark. And, of course, she stood up to Katherine in defense of her "sister-in-law" Pam. Can you imagine the little b**** who slept with JR at Lucy´s wedding doing that? Too bad Audrey Landers didn´t like that change and that, obviously, they didn´t want to get deeper into Afton´s change and just turned her into Cliff´s doormat.

Rebecca was always an underwritten character, at least between her debut and Cliff´s suicide. Then she went all extreme and wide-opened. Almost like Angela Channing on acid. I can´t remember one scene when she and Cliff talked about Sue (aside from that one from "Missing Heir"). Of course she seemed to live in oblivion and follow the "look away" style of her "friend" Miss Ellie. In real life, Rebecca would have liked to meet Sue and check out if she was being "good" to her son or just "gallivant around town again".
"Hmmm. Hairdo, butch. Clothes, The Store.
Needs a teeth fixing".
I don´t think that Katherine met Sue by then or that she gave a damn about Cliff´s personal life. But it was then when the seed of "wickedness" was planted and gave us a couple of great years with her. About Clayton, I honestly think that he never had serious feelings toward her, he just got influenced by that mean-spirited girl from Biloxi. That twist made Clayton look a little dumb, I´d say.
About the affair in future seasons, actually Sue did try to resume it in Season 12. First she told that awful April about it and then she met Cliff and hinted they could make JR suffer again. Luck Cliffie had learned something and become a bit smarter.
"Sure you don´t want some good rimming?"