If there were a general org export option to do so I would expect to see it documented here: http://orgmode.org/manual/Export-settings.html#Export-settings. Looking directly at the source for I don't see an option in the markdown export engine to do so either.
If you are looking for the Quick-and-Dirty Solution™. You should probably redefine the org-md-link function to "format" link strings according to your preference. For example replacing
(format "[%s](%s)" contents path)
with
(format "%s" contents path)
I agree with you the option you are looking for would appropriately belong in the core export engine, so the translator of the selected export engine wouldn't even get called. Kudos to you if you submit a feature request (I would +1 that). If you do submit one-- post a link here for others to track it?