They should have some regulations like only the creator and 'approved' members are allowed to change things and/or a log showing who changed what (very important if you don't want Batoto to become a consequence-free environment, like how wikis keep things in check). Ever since I realized that anyone could change things just like that I saw this coming, if not someone going ahead and replacing all the pages with porn (if actual chapters are unregulated as well).
Or maybe show both, though I'd rather have chapter count. Sometimes I'd dip around in certain genres, see a nice name and pop in...only to have it span one whole chapter. It's really annoying if it's a series which got dropped after a chapter or is still in work since I know if I read and happen to like it, I'll be forced into a cliffhanger (not counting one shots ofc). It would really save me some time to be able to sort by length and then browse down the list so I can get a nice chunk of reading done.
There are obviously technical problems like chapter count of other languages and repeats but I don't think it's flat out impossible and I can't see why it would be 'ethically incorrect' to implement. We already have a rating/view/follow system which 'encourages' popular manga to get more popular so chapter count (which does reflect popularity in some cases) wouldn't make ignored mangas even more ignored.
Most mangas accused of netorare, while may indeed contain elements of it, often have the protagonist "take back the love" (Ai wa Torimodose?!). A popular method for immersion is simply pissing off the reader and then granting the satisfaction of revenge. A very effective way to piss the reader off is to steal (as in steal the relationship, not just physically capture) the protagonist's lover which, without the revenge part is NTR. I guess it's easy to assume any manga which provokes frustration or creates some feeling of loss is NTR even though it doesn't involve any 'cheating' on the protagonist (which tragedies do a lot and are aptly tagged).
I believe hardcore NTR preserves the despair to the ending, never giving the protagonist, and anyone who empathizes with said character, anything but frustration. While it's true this seems to be a solid rule, it depends on how sensitive the reader is to this sort of psychological bullying and how 'satisfying' the outcome is. If the reader decided to stop reading and miss the ending, then what was read could qualify as 100% NTR.
I agree with thearux though, the Drama (Tragedy too in some cases) tag pretty much covers and it, just as Romance covers the disputed topic of incest. That being said, Drama is too broad and many blurbs make a point that incest will happen (if not the cover page itself) while NTR is almost impossible to see coming without spoilers (since the protagonist is implied to 'lose') unless there is little to no plot (aka porn). Perhaps a 'Bad Ending' tag is in need? I jest, there's no real concrete solution.
However, here's something worth taking with you:
Devoting feelings to a plot is asking the author to play them like a harp. If you aren't prepared to lose, don't invest.