For a practical example, the camo uniforms during my brief service (mandatory in Finland) came in all sorts of worn-down variants. Generally, they had little in the way of decoration, being for rough'n dirty field use only - rank markings in the collar, but nothing else, no unit badges or anything like that. But there were situations where a name tag would have to be worn, and it had to go "over the heart".
A dozen ways to do that, with the half a dozen uniform types handed down from previous generations of users: the ones with chest pockets sometimes had these pockets in a location suited for the "over the heart" positioning, sometimes not, and sometimes a type of uniform that was supposed to have the chest pocket over the heart had this pocket missing due to wear and tear. There would have been no point in regulating the placement vis-á-vis the design or status of the uniform; "over the heart" was more than sufficient.
Starfleet uniforms are a bit more uniform - but Starfleet personnel are not. There would probably be similar leeway simply because three-handed people would need
to place the thing differently, and never mind people shaped like turtles. Dedicated rules for humanoid-shaped, turtle-shaped and shapeless crew might well be a silly idea. Especially when we remember all those occasions where a commbadge was not worn at all: apparently, there is no solid rule about that