I commented on this answer some time ago regarding how visual studio comments out code with // or /* */. I was thinking to revise the answer (to include my findings) but I had to test it first, which kind of confused me.

My finding is that depending on where your marker is when you press Ctrl - K, Ctrl - C you will get either // or /* */. So I tried it out on the following code:

[1] [2]FD_ZERO(&mFSet);
FD_SET(user->mSender, &mFSet);
timeval zeroTime = { 0, 0 };
int sel = select(0, NULL, &mFSet, NULL, &zeroTime); [3]
if (sel == SOCKET_ERROR){
    [5]return false; [4]
}
if (sel == 0){ [6]
    return false; [7]
}

The [x] is markerpositions. All [1] positions give // for all marked lines. However

• Start position > End Position: gives:
• [2] > [3] : /* */
• [2] > [4] : //
• [2] > [5] : /* */
• [2] > [more than 5] : //
• [5] > [6] : /* */
• [5] > [7] : //

I guess it has to do with forward indentation (not backwards), that whenever code is indented more than the starting line you get // except when you haven't selected any text on the indented line ([2] > [5]).

But why the distinction? Why not use /* */ for when you start at [2] and // when you start at [1]?