I have a few things to add. I have a number of allergies - coeliac is one.
In terms of absolving themselves of the right to be sued for negligence - you can’t actually waive your right to this. If you had a peanut allergy, and you identified yourself as such, and they put peanuts in your food and you died, this piece of paper wouldn’t help them.
HOWEVER - you have to risk assess the situation yourself. There will ALWAYS be the risk of cross contamination in any kitchen which isn’t fully gluten free, so that in itself is somewhat of a red herring for a coeliac.
For me, I judge it on how aware of and how seriously a place seems to take food allergies and how knowledgable the serving staff are. It’s very obvious, very quickly. We have politely left many places - if I don’t feel comfortable, I won’t eat there.
Coeliac is very serious and cross contamination is an issue, but you also have to be rational. It’s not airborne. If I had an airborne allergy, I wouldn’t eat anywhere that couldn’t guarantee no cross contamination. If I had anaphylactic reactions, I certainly wouldn’t, and to be honest I probably wouldn’t even eat out.
You have to ask them specifically whether they use a shared fryer - that’s the thing that often does get forgotten by staff. Shouldn’t, but does.
In terms of them humiliating you with this clipboard and sheet to sign - they are showing themselves up, not you. They have tried to ‘cover all bases’ in terms of litigation, and just failed. It just makes them look ill educated, and a bit silly!
If they don’t feel that they can safely prepare food for people with allergies, then they shouldn’t do so. I understand it can feel awful, I’ve been there myself - but ultimately, these chefs and waiters are potentially playing with people’s lives and being paid little more than minimum wage for it. If I couldn’t be certain, I wouldn’t serve me either - it’s their conscience involved if they get it wrong - and more importantly it’s someone’s life. If they have a small kitchen serving mostly sandwiches or fresh pizzas for example, the place will be full of allergens for a coeliac. They won’t have space to keep somewhere totally safe.
I know it feels like you’re walking round with a big X on your forehead sometimes, but it’s better to not be served in a place that can’t serve you safely than to be served and them get it wrong.