Avira > stories that have a message or torah value are not devorim batailim,
Glad we agree. R Twersky quotes Beis Halevi who observed 3 horses with carts going in a convoy. Each horse would eat a little from the previous cart. So, horses 1 and 2 benefit by having lighter load, and horses 2 and 3 benefit by eating. So, horse 2 is in the best position. Beis Halevi concludes that this illustrates the Rambam’s middle road approach is the most beneficial, rather than taking extreme positions (a lesson for CR also). R Twersky’s meta-comment is that Beis Halevi can learn mussar from the horses, while some may read mussar books many times and still not get it.
So, maybe it depends on the reader – if you learn mussar from tintin or peanuts, it is mutar. If you learn shtus, then comics are assur and maybe even other books.