Topic: Have Bitcoin's consensus rules ever been changed? (Read 451 times)
Certainly. The consensus rules change with any fork, be it hard or soft. All planned forks to date have been soft forks. To see what these are, look at the list of BIPs: https://github.com/bitcoin/bips/blob/master/README.mediawiki. Anything listed as "Consensus (Soft fork)" and has a status of "Final" are all of the BIPs for soft forks that have already been activated.
if so, how often, and on what?
every time on soft-fork activated 
if so, how often, and on what?
Jump to: