It’s mentioned in the Markdown format that you shouldn’t use / in your intent names, because it’s used for the response selector intents. Other than that, I don’t know of any other restrictions.
With regards to entities, because they’re in the [value](entity) format, I could see parenthesis perhaps causing issues, but other than that, not that I know of.
I used a bunch of characters in a very long string (I wonder if there is any character limit for intent or entity) for the majority of the intents due to the design that we chosen here. Characters like ‘(’ or ‘.’ were OK in the intent name.
I am working with the json format and had a problem regarding the declared position of the entity and the true location of the characters, only when using the character ‘/’ in the value of the entity, but I think I only got this because of the choice of the spacy tokenizer.