I don't really agree with the other answer.
I strongly advocate for avoiding spoilers in titles except when they are really, genuinely, 100% necessary for the post to make any sense. Keep in mind that when you google for an answer to some anime-related question, google indexes both the title and the body of the post, so stuff is still findable even if you're somewhat roundabout in the title. While I imagine the title is granted more weight, avoiding spoilers in the title still likely does little harm. I think that the benefit of avoiding spoiling users' experience with various shows outweighs the cost of losing some descriptiveness in the titles.
I also want to point out that while the claim "the ignore tag feature will allow users to ignore any tags in a series they wish to avoid spoilers about", is technically correct, it does not propose a practically useful course of action. Here's why:
Suppose that I'm Joe Blow, some dude who's only seen Naruto. One day, I come to Anime.SE and ask some questions about a Ninetales Uchiha Hokage Rasengan. While I'm here, I see some questions on the front page about this thing called "Death Note". That sounds like a pretty metal sort of thing, so I figure I'm going to go and watch that when I get a chance. But! As I'm browsing the front page, I see another question title that reads "Why did Rem kill L?" that's tagged with [death-note]. And then I watch the first few episodes of Death Note, and suddenly the context of that question becomes clear - I know who Rem is, I know who L is, and now I've been spoiled on the fact that Rem is going to kill L at some point!
There's the problem - users cannot, practically speaking, ignore tags for all shows they may want to watch in the future. If you know in advance that you want to avoid spoilers for X, sure, ignore [X]. But if you don't, what can you do to avoid spoilers? If the spoilers are right there in the titles, there's effectively nothing you can do. And that's the problem with putting big spoilers in titles.