I think we've got to be cautious about saying "most triggers are obvious." Because of how trauma and mental illness work, most triggers are probably the random, non-obvious kind.

(Also important to note that "triggers" are different from just "finding something uncomfortable or squicky." Although it's good to take both into account when thinking about warnings.)

And even with common upsetting topics, not everyone will come up with the same list before posting a fill. A lot of people are squicked and/or triggered by infidelity -- and once you think about it, yeah, it's obvious why! But nobody in this conversation has mentioned it until now.

Which is why it's so valuable to have a specific list of "these are the topics that require warnings in this space."