The Fire Marshall has referenced ICC A117.1 608.2.2.3 Seat (in shower)

Shary, my response to this issue (which is on every project!) is the same as the one you provided. Unfortunately, to my knowledge there is no code language to support the ligature risk exception. Instead, you could reference the hundreds of times TJC has cited a shower seat as a ligature risk. ADA accommodations are still provided to every patient that needs it.