Right, I guess that sort of rewriting of CRUD situations would be nice in some cases.
Although in real applications, most of your methods are complex enough that you'd want them to be multiline blocks, at which point it would start to get really ugly IMO.
Anyway it sounds like I'm being more critical than I actually am I think.
But my un-DRY annoyance with Sinatra isn't writing multiple blocks with route declarations for CRUD methods, so much as not being able to refer to those routes in your views abstractly. ie., if you decide you want to change from /comments/:id to /awesome-comments/:id, it's a headache.
I assume there are plugins to fix that annoyance, but I'd have like Sinatra to generally have routing more abstracted from specific URL paths.