This is not a question. I am new to chemistry stack exchange and I don't know how I can report a bug. Hovering over the "favourite question" button always pops up a message saying"This is a favourite question" even if it is not
I think this is intended, it's just slightly bad wording. What it says is:
This is a favourite question (click again to undo)
I interpret this as saying, if you click this button it will be a favourite question and if you click it again it will be unfavourited. I agree that this is possibly not the best way of expressing it, particularly if you are not a native English speaker.