The ignore a user-function (not matter if eMail or wiki-notifying) is not working at the moment. To be more precise: It is not possible to add users to the ignore-lists.
How to replicate (all tested on the German Wikipedia):
1.) Open your preferences-page.
2.) Scroll down to where you can enter the users to ignore.
3.) Add a user-name successfully.
4.) You can NOT save your change (the save-button remains grey). If you change something else on the page, the save-button turns blue and you can save your edit. But the user-name you just added is gone when you reload.
Just to let you know.