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Newbies should not be able to disable, and probably even fulls, but maybe seniors or heros should be able to disable this. ADs on the site should definitely since we already have the option right now.
You want to compare a newbie account with an higher forum ranks, everyone must have the right to/or not disable some signature and seen other signature. Where is the freedom of choice? The problem here is the "users" that "make" a lot of insubstantial posts and the definitive solution is not only to "disable" some signature (they will continue probable to "make insubstantial posts"). I haven't a final solution but this is my personal opinion.