I think I found something out based on the experiences from some anons here and my own; Tavern and Gradio pygmas accept different formatting. Gradio pygma is fine with CAI regular (almost) formatting but gets finnicky with W++ style formatting of descs and chats, whereas Tavern would rather have you use W++ instead of CAI formatting. Gradio makes the bot pull out a random {([s and plaster it on the reply of the bot if you have it formatted with W++ or even just the normal "{{user/char}}" thing in the dialogue examples. But Tavern is fine with all of that but might end up throwing a random excerpt of the description of the bot on the chat or even the entire thing (see this anon's post)
>>42550963 if you use normal text formatting or CAI instead of W++. I feel like there's more and this is only scratching the surface of it. I don't even have time now because I have things to do soon enough, once I'm done with that stuff I'll start experimenting with this myself and check the proper way to format bots in either.
tl;dr Tavern and Gradio accept different types of formatting and clash with each other.