Firstly, not all soft forks introduce extra data. Some are simply about minor policy. Second, soft forks have been the standard since the beginning, and everyo

Firstly, not all soft forks introduce extra data. Some are simply about minor policy. Second, soft forks have been the standard since the beginning, and everyone understands that minors can set their own rules. Third, non upgraded nodes, if they follow the longest chain, do not break. If they mine themselves they'll get orphaned, but that doesn't break them as long as they wait for a couple of blocks before accepting transactions as valid. Fourth, soft forks have traditionally repurposed non standard transactions, which shouldn't be issued by anyone expecting consistent behavior. Segwit uses anyone-can-spend which are non standard, and as the bip says "Wallets should always be wary of anyone-can-spend scripts and treat them with suspicion." Fifth, anyone can "notice" by virtue of the block header changing. A majority of minors can reject transactions, that's not deceitful in any way.