Neuvillette feels guilty but it does not haunt him. I like to HC that he wondered for a while, how he could have made it gentler, privatized the trials, etc. But in the end, they both did what they thought best during a time of crisis. Because Furina doesn't fault him, his guilt is lessened. I think it'll take some time for him to process it fully, but I don't think it'll haunt him. Haunting regrets isn't something I attribute to nufu~