I take it to mean “without proper fashion sense, recognizable by any target reference class”, rather than the more typical phrases “dressing down”, which means to be less formal, or “costumey”, which would be trying to fit a particular style very closely.
It’s not clear what you mean by dressing “badly”. I’d agree that it can be advantageous to dress “badly”, as long as you do it right.
I take it to mean “without proper fashion sense, recognizable by any target reference class”, rather than the more typical phrases “dressing down”, which means to be less formal, or “costumey”, which would be trying to fit a particular style very closely.