I made this suggestion ages ago:
http://news.ycombinator.com/item?id=1012215
The idea is to use just the first part of the URL, and then to use the extracted title. Seems much more reliable - I use it to auto-detect duplications. It annoys me to have the same item submitted over and again, mostly because it splits the discussion. For me, most of the value here on HN is in the comments - often the discussion has more value than the original submission.
I suggest you paste the URL with random text as a title. If it shows up as a unique new submission then update the title immediately with the original. If further tweaking to the title is in order then follow-up again.
But yeah, its a pain when it happens but its not very high up on my list of grievances.
Given the choice of eliminating problems on this side it would be getting people to put "Ask HN: " in front of questions.
You would mostly run into a problem if you are submitting a blog post that is talking about something that is already on HN.
Sob.