Is this practice defensible?
Obviously, since people have defended it. ;)
Perhaps the real question is down to whether the defense is justified.
For my part, I'll search a post for '?' and if the first hit is ..
Know someone who can answer?
(N.B. Directly quoted from StackOverflow, which itself seems to fall into the same 'not a sentence' area.)
.. I will scan the post for a goal then directly, put 'How to' in front of it, and a '?' at the end. I deliberately choose not to alter the goal in any other way, in some sense as a way to indicate:
Look how easy it can be to turn a goal into a question!
OK - not for the 'grammar conscious', but then, there are not too many of them who make comment in any group other than this one.
English is an evolving language. This is a very good example for change. If "How to [goal]?" is not a valid question then it is English that should change.
Am I being unreasonable?
IMO (for whatever little it is worth) yes.