This is not equivalent to a newspaper advertisment because a newspaper isn't online content (though it's close enough that an argument could be made on the inve

This is not equivalent to a newspaper advertisment because a newspaper isn't online content (though it's close enough that an argument could be made on the inventive step). However, there is definitely potential that this is novel. I was going to say that there is also no method of changing a user comment on a newspaper after it has been created, but on a second inspection of the claim, there's no requirement for this within the claim. And based on that, I think you may well be right that there is a good chance of invalidation, because the system boils down to a system where one can place advertisments on specific parts of a piece of online content and being able to pay more for a better looking ad.