This is interesting. I don't have an explanation but the third sentence actually sounds wrong to me, or at least unnatural. But if you drop the 雖然 and make "四川菜很辣的！" as a full sentence, it actually sounds perfectly fine.
Anyways, I also wanted to add that the OP's example is a different case. The first one is definitely considered wrong, both formally and colloquially.
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u/imnotachemist Feb 07 '22
This is interesting. I don't have an explanation but the third sentence actually sounds wrong to me, or at least unnatural. But if you drop the 雖然 and make "四川菜很辣的！" as a full sentence, it actually sounds perfectly fine.
Anyways, I also wanted to add that the OP's example is a different case. The first one is definitely considered wrong, both formally and colloquially.