Lets say I have a website, twitter, that I load more often than any other website. It is my first tab. Let's also say that I have a bookmark of an imgur url with a 't' in the random url string and a title of 'this cat'. When I type 't' into the location bar, the first suggestion is my bookmarked imgur link. I highlight it and use shift delete to remove it from the bar and select 'twitter', which is the new first suggestion. I open a new tab, and type 't', the deleted bookmark suggestion is again at the top. I'm not sure if the bug is the location bar not respecting delete or if bookmarks are weighted too heavily.