Is It Libelous to Accuse BDSM Participant of Having Hand Tremor and Vision Problems,

and thus not being able to safely participate in BDSM activities (presumably on the dominant side)?

Not a hypo! See Zeglam v. Infliction Hall, No. 348-340484-23, filed Thursday in Tarrant County (Ft. Worth area). There's also a #TheyLied libel claim based on allegations that plaintiff had "committed … sexual assault" and more generally "violated consent." An excerpt of one of the allegedly defamatory statements:

"you had expressed concerns about not being able to get people out of rope because of your hands and that you were not sure if you were safe to tie earlier this year according to text messages. I was also told that it was not safe to do impact with you necessarily as there was concerns about you missing your mark due to I believe the tumor you mentioned…."

The legal issues are the usual ones in libel cases: The allegations of sexual assault, if false and stated to someone other than the plaintiff, would be potentially defamatory. The allegations that one has done things that are potentially dangerous to others while lacking the requisite physical ability to perform them safely would be potentially defamatory, too. Much would depend on the sorts of damages plaintiff could prove, and on whether defendants' falsehoods (if they were indeed false) were knowing or reckless, or were negligent, or were just reasonable mistakes. But in any event, this is a good illustration that libel claims can happen in all sorts of contexts, whether Mensa conventions, the Society for Creative Anachronism, the doula profession, or Infliction Hall.