There's the same 'feature' which works against insightful commentary. Spend too long crafting a response, get "unknown or expired link". Not particularly endorsing of a considered, pensive response.
Surely there are better ways. For example, you keep track of which posts a user has already seen, and when they hit the next page button, show them the X most highly ranked posts that they haven't yet seen. Breaking the link is just the easiest way to deal with the problem.
I don't think that's a bug, but a feature - a type of cache invalidation that forces you to refresh to ensure paging is accurate