Heather L. answered 04/30/19
Experienced Spanish and English as a Second LanguageTutor
"Very interesting" can be both a positive or negative expression, depending on the context. If I watch a documentary and find it compelling and I want to learn more, I will say "That was very interesting!" in a positive sense. However, if I am puzzled by or have doubts about something I see, read, or hear, I might say "Very interesting" with an intonation which implies doubt or question.