X mirror behaviour inconsistency

X Mirror option is saved per object not as normal tool settings (auto merge)

Save option with the object is very dangerous and may leads to destroy your model. Because you simply don't note that it is turned on. Imagine that you have big robot with many parts and some of them has turned on this option. Tool settings panel is hidden by default, so you can not even see it.

I lost lot of work due to this behaviour.