This may be a little OT, but if a person was dead set for some reason
on venting to the attic OR they came across such a set-up, you can
simply change your habits to minimize risk of attic condensation.

For instance, don't run your fan when it gets chilly enough outside to
see your breath (or thereabouts). In cold weather, heated interiors
experience a drop in humidity and can absorb lots of moisture without
the humidity getting high. It may be a good idea to run your
forced-air furnace and keep the bathroom door cracked when you take a
shower to keep an influx of low-humidity air into the bathroom. In the
winter, I can take a shower without running the vent fan and the
mirrors don't even begin to "steam up".