I’m going to quote BoilingOil, because I’m not familiar with it myself (having never experienced it in my own game):
“The Debug Super Duper Hug is a special autonomous testing interaction that allows any sim to hug any other sim without the fear of being rejected. This hug is very effective and make sims into friends very fast. Some people [modders] use it as a template for creating new interactions, where the original is kept on as a fallback. When such a mod is later removed, the Super Duper Hug is then introduced by the game to compensate for the missing interaction. My No Sim Loaded mod protects against this annoying phenomenon.”
Basically, your Sims will keep going around trying to give hugs. From what I’ve read from people who had it in their game, it is incessant and annoying (and as iCad pointed out, may cause your Sims to make a lot of enemies if the hug gets rejected). It’s more of a nuisance than anything – it won’t break your game or cause neighborhood corruption. But for some people, having a buggy game in any terms is (understandably) unacceptable. For me, personally, if there’s no long-term damage and there’s a fix to suppress it, I don’t have a problem with it and I’m not going to go crazy reinstalling and starting from scratch. But it is incredibly viral and spreads through lot downloads, and once you have it you always have it. So if/when I share lots in the future, I have an obligation to let downloaders know of its presence (and, of course, link to the fix, which everyone should have in their game already, bug or no bug).
Downloads are still offline for now until I add a disclaimer to all of them…