Then it is not a TODO, it is a NOTE. Don't act as if it will be _done_ magically in the future. If I stumble upon a TODO, I won't fix it (because it will diasrupt my flow - the reason for the TODO in the first place). And if it is not in the issue tracker, I can't plan for it. A solution would be some kind of an "implement as many TODOs as possible" time-boxed spike, but this never worked really well for me in the past.