"The writer mentioned although it deals with eastern mysticism and sexuality, the content is not erotic." - This is a sentence I am copy editing. I am under the impression that "mentioned" should be followed by "that" in this sentence. Could you please let me know your thoughts on this as well?
When I wrote about this to the person who wrote this sentence, this was their response "I have checked it through several proofreading sites like Grammarly, Paperrater, Scribens, etc. The sentence is correct with or without inserting "that" after "mentioned."