I have noticed that shortcuts such as (command + v) do not work in Minecraft for mac. Instead you need to copy and paste using the ctrl key. This is counter-intuitive as the information you originally copied would have been done so with the shortcut (command + c) then would have to be pasted with ctrl + v.
Duplicate of MC-2292 - If you have not, please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.