The GP's point is that the default engine, and hence the one used by probably 90+% of people using MySQL doesn't support FKs and other "standard" data integrity features that you wouldn't even know to ask about, since every other major db supports them by default.
Plus if you try to create an FK on a myisam backed table it happily runs the SQL, without errors, and you think you have a working FK.
It's more like the "default default" -- you can change it so, by default, every table is created using InnoDB. IIRC, MySQL comes with an example config that demonstrates just that.
create table foo (blah, blah, blah) engine = innodb
Sorry, I'm not trying to start an argument. That sentence just struck me as a bit inflammatory.