The more people use the word 'trigger' to mean 'upset', then the more the word will start to be completely synonymous with 'upset'.
And then , someone will need to come up with a different word for 'trigger'.
Other places, like my specific example I gave in my first post, they would have already seen the content before they would see a content warning if you did it like that. Or they might not see the content warning at all.
Well, on Tumblr - I believe that was your example - I often click through to the 'homepage' for the blogger, and in that little bit of space up there at the top, get enough info for what I'm about to see. Americans are very accustomed to "Warning: this material contains graphic violence and nudity. Viewer discretion is advised". Live performances carry warnings for strobe lights, gunshots, smoke...almost anything that could cause someone to have a stroke, seizure, asthma attack, and they are expanding into things like warnings for nudity, gore, violence - things that might cause a person with mental health issues to have an anxiety, panic, or flashback response.
At a certain point, as a person in the world, you need to decide if there are just areas you must avoid at all costs. And if someone accidentally clicks on an image in your blog that freaks them the f*ck out, I am sorry for that occurrence - but there's no way you can take full responsibility for that.
I think hashtags have actually helped matters, because people list individual attributes. In my own trauma diary I generally will say "the next bit is going to be about graphic description of rape and mutilation, so if you don't want to see that, move along". That's all I believe I'm responsible for, and I personally think it's just a nice thing to do. But I also absolutely support that it's not necessary. If people read the terms when they join, they'll know that there aren't going to be big flashing 'trigger warnings' everywhere, and they should move at their own pace.
So, just coming back around - I think that the process has already begun, where 'trigger' is shorthand for 'will upset', not 'can cause a visceral reaction that may cause your whole day to go to shit'. So, more complete descriptions of content are the way to go.
And perhaps, it doesn't even need the word "warning" anymore.
When a piece of writing is called, 'Penguins, the Good, Bad, and Ugly' - if you are penguin-phobic (to use
@lostforgottensoul's example), you should know to steer clear. Saying "Warning: this story contains penguins" is a little silly. But if it's 'Ponies and Lollipops', and happens to contain a description of a penguin massacre, then 'This story contains graphic depictions of penguins, dismemberment, and gore' - well, that would be good to know. Especially because it was called Ponies and Lollipops.
So, context and content, and detail - these things will always (in my opinion) be more effective than 'trigger warning' or even 'trigger warning for rape'.
Especially on a story/post/piece of art called 'My Rape'.
Which is kind of what it's devolved into, in terms of over-application.