I sometimes forget that I've added a task previously, and I write it down again (usually happens on mobile, when I am on the go). I then end up with 2-3 instances of the same task, written the same way or slightly differently.
I find that it makes the backlog a little messy, and I wish there would be a feature that can bring up similar or identical tasks when I am writing down a new task.
It's more of a convenience and quality-of-life feature, but it would help me stay clear with what I need to do.