Discourse is more flexible than that; there's almost certainly an option for minimum characters in posts/titles. I think there's some discussion about changing it already, but the general reason (I believe) the rule is automatically implemented is to ensure that posts are constructive.
It makes sense, when you think about it. For example, in this post, ‘CE 3’ as a title is extremely vague. What about this “CE 3”? Is it a discussion thread about the events of CE 3? Is it a critique on Tacticsoft's handling of CE 3? ‘What Tick Speed Should a CE 3 Be?’ is a much more informative title.
And then there's the old forums, where about 75% of the responses there are either “Lol”, “Soon”, or “No”...
Personally I'd disable the character limit for the Spam section and any others where constructiveness and information aren't a concern, and keep it for the rest. No way to edit the poll to add a ‘Tweak’ option though.