Cool, thanks!

Who does the tagging by the way? You, or users? (Basically, how likely are other chapters to be tagged like this?)

In general, I think that the "kissing", "nsfw" and "almost nsfw" will always be spoilers, at least in series (a sudden nsfw tag at chapter 10 would be a spoiler, while a one shot tagged nsfw is something pretty usual). IMHO, "kissing" would be a spoiler even in a one shot: it distinguishes between good and bad ending one shots, bad ending being relatively common.

I'm sure there are a few other spoiler tags. I'm sure you don't have anything as blatant as "confession" or "death", but maybe "NTR"?

Another possibility would be to not display any tag for individual chapters, only those for the serie as a whole, thought that might be too strict.

First, thanks for the reader; it's amazing, and I love it.

That said, consider for example this page:
http://dynasty-scans.com/reader/series/flower_flower

See that tag on chapter 13? Do you see how that can be considered a (major) spoiler?
So okay, the tagging could be trollish, or not represent exactly what it looks like, or something, but still.

So my suggestion would be to hide tags by default, at least on the http://dynasty-scans.com/reader/series pages. Actually, even on the "recent releases" page it can still spoil a lot.

Again, your reader is awesome, and this is a minor point. Also, sorry if this has already been debated.