This would really help when capturing ideas on our ideas portal.
I regularly have to review lengthy descriptions which have been added as ideas. I'd love to be able to restrict how many characters my users can type into 'description' fields, so that I can encourage focus on the important points (rather than 'ramble on and on'!).
We are unlikely to work on this idea in the near future. However, we do recommend that you use a template for idea descriptions to help guide your users.