When bracketing crosses the line into abuse
Not all bracketing is abuse. A customer who brackets twice a year while they learn your sizing is a fit problem. A customer who brackets every order for two years is using your policy as infrastructure.
The line is pattern and intent signals. Abuse shows up as bracketing across every category, returns timed to the end of the window, kept items concentrated in one size while the same bracket repeats, and zero adjustment over time despite size guidance.
There is also a harder version: bracketing combined with wardrobing, where the kept item comes back too, worn. At that point the customer is not solving for fit at all.
Brands that score return requests per customer can act proportionally. Occasional bracketeers get better fit content. Habitual bracketeers get warnings and then policy enforcement. Everyone else never notices a thing.