When you start mining stones or wood or anything else with LMB you don’t need to keep it pushed. Simply start mining with LMB and then open inventory with “I” button. Your hero will be now automatically mining until you select other function (and you can close inventory), or your tool brakes (probably even then hero will be swinging with bare hands…). Now you just have to move your hero to the next stone/iron/coal etc.
How is that an exploit again? And what does it do an “autofire” doesn´t do?