Originally Posted by oneclick

I don't like that dent. Top-tubes are loaded (mainly) in compression; the crease is favourably aligned to initiate a buckle. And it's big. It's big enough that you should take a straightedge and check the tube.

Get some frame blocks and fix it. They're not expensive, it's a simple job that goes slowly and it's pretty hard to make things worse even if it's your first time.

However, if you do it yourself the paint should come off down to bare shiny steel, if you leave paint on it will be torn up anyway, but that's not the problem with leaving paint on. The problem is that the blocks work by having the high spots of the steel surface slide inside the block as they compress downwards, with paint on they stick. Shiny and loads of grease.