Ok, that last bit is a good point - I'll take out the question mark. Thanks!
Re your other question, the short answer is somewhere in the space demarcated by (1) yes, (2) we'll try, (3) consistency is impossible, (4) we're always open to reader input.
This seems a little partial and hard to implement consistently. Can we assume the same metric will be applied to every Robert Woodward story, or any of many single-sector journalists with a lengthy track record, such as Radley Balko who has spent years writing about policing?
I also don't think adding a question mark to the headline clarifies; I can treat an assertion with skepticism, but 'How America took out the Nord Stream pipeline?' reads like a submission from a non-native English speaker, of the sort which often clutter up the New submissions page.