When I view any normal site on a Macintosh using Safari, Chrome or Firefox, Command-L selects all the text in the address bar, allowing me to navigate somewhere by URL. This is similar to Alt-D, the command for going to the search box right away, which Jeff had mentioned he likes in a podcast.
I get a little annoyed when the Markdown editor overrides that for creating a hyperlink, especially if no text at all is selected in the editor. Could that key combination be made to work only when text is selected, leaving people who must do it with no text selected to click the icon?
Do you have the capability to track how many users actually type in links, use Markdown by hand for linking, use the link button by clicking on it, use the key combination with text selected and use the key combination with no text selected? Is there some spike in the latter with users of say, Chrome (where the address bar is also the search box)?
Update
If the data, assuming they exist, suggest that people on Macs are using WMD shortcuts erroneously (e.g. pressing Command-L and then Cancel) more than other platforms, I suggest, in agreement with the answer below, that the option to use the WMD with Command modifier key combinations be removed, and notice given that the Control modifier key combos remain in operation.