1. The same story often appears in different versions: different news sources, different posts of the same story, different dates and times of posts. To what extent they comprise "duplicates" will always be in dispute.
2. Sometimes headlines will change without the story proper changing. This is especially true of wire-service dispatches, and stories in The New York Times (don't ask).
3. Even the slightest variation in spelling or punctuation can prevent a story from showing up in Search.
And agreed, headlines should not be in ALL CAPS, but some sources (notably Drudge Report) headline stories in caps. Correct the case size and you risk running a duplicate; use the caps and you show off.
This member will always try to do his best to keep his fellow members informed, and to adhere to the reasonable rules. But please realize, as I trust you do, nobody's perfect.