From a bug report: attempting to apply
a towel which is currently "worn" in the weapon, alternate weapon, or
quiver slot fails with "you cannot use it while you're wearing it". The
message sounds odd when the towel is wielded, and there's no reason why
you shouldn't be able to use it when it's in any of those weapon slots.
Compare it with current blindfold rather than checking its owornmask.
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