That's a bit of sophism. Anything can be confuted by disagreeing on its definition. By this reasoning, spoilers themselves don't really exist. However, what we do have is direct experience, that tell us that a large chunk of people like the idea of not knowing anything about how a story will end. I do know what "tragedy" is about, in fact I did specify that it's sometimes its charm. However, if we're really going by the book definitions, that is referred to ancient Greek tragedies, which are a completely different genre on their own.
"Comedy" is very different: it just tells you what it's about, not how it ends. A "happy ending" in a comedy is a different concept, and it's not spoiled beforehand. Of course you know nothing terrible will (again, usually) happen in the end, but that's not enough to define a happy ending in that genre, while it might be to define a happy ending in "Horror". As for "horror", you go in to be scared or exactly to witness terrible stuff happening, the intention of the reader is different. But tragedy, if we're not talking about classic tragedies, doesn't define the story's theme. That's what the "drama" tag is there for. By the way the tragedy tag is used most of the times, its counterpart wouldn't be "comedy", but something along the lines of "upbeat". If, instead, we are using the "tragedy" tag to follow the original definition of the genre, I don't really know what it's doing there under some titles like

Fullmetal Alchemist , where the point isn't to present the readers with tragic events to trigger a cathartic feeling in them, but to show the characters' struggles to give a feeling of accomplishment. Long story short, "tragedy" as a genre is when you'll willingly witness the terrible fate of the characters to achieve cathartis (think of Aedipus), "tragedy" as the modern concept is more like "something really bad happens", which is really akin to a spoiler in my opinion. This is definition on this site, by the way: "Contains events resulting in great loss or misfortune".

Anyway, I really went OT on a dead thread for way too long, so I'll end it here.

My current top 3:
Fullmetal Alchemist
Pandora Hearts
3-gatsu no Lion

I would also like to have the option to not see the tragedy tag. Whenever I see it I feel like the story got spoiled.

The problem here is that by the logic some in this thread are using, not just the tragedy tag but all of the genre tags, the synopsis, heck, almost everything on the series page could be argued as a "spoiler" (and no, not singling anybody out, this flawed logic goes back to the beginning of the thread).

This kinda boils down to looking out for yourself here.....if it's really a big problem to some, they should really just be a little more careful when they're going to the series page to begin with. Nobody's really thought out just how something like just one word is going to be somehow magically not shown, right?

I mean, seriously, think about where this could lead........putting every single little thing on the page in spoiler tags like was done with the category tags? The image too? The synopsis? The ratings? The recommendations?

Sounds a little ridiculous, doesn't it?