I use the built-in Command+D (or Control+D for the Winders) to handle this in a slightly more manual way. Sublime is less "scope-aware" to minimize bloat, I think -- not to discount your need for the feature.

When I work in XCode I constantly miss Command+D since I find it more flexible. 

Though I will admit that Control+Command+E for Edit all in Scope in XCode is really really handy and I also use that in Sublime Text (which luckily doesn't do anything).

Similarly, the shortcut keys seem to be very different on OS X versus Linux/Windows. Is the reason for this just because PC users are accustomed to Notepad++ or gedit or is there a more practical reason (except for the Command / Control switch)?

I switch between OS X and Linux a lot, so this difference drives me crazy. 

THIS! I write a fair amount of JavaDoc format comments in my larger projects, and sometimes I just need to write a comment that is a few lines in the code. I would love this feature or at least a way to add it with snippets. <tabTrigger> doesn't quite cut it here.

Note: As a temporary solution, I just write them with no * at the beginning and then do a multi-line select (Cmd+Alt+Click-Drag) at the beginning of the lines and type " * ".