[ietf-dkim] If DKIM would ignore [] at the beginning of the subject line

Silly question (?): 

Knowing that many mailing lists add [topic] at the beginning of the Subject 
line, what if DKIM was set to ignore that part when signing/verifying? 

Would it help to solve the problem of broken signature thru mailing lists? 

I realize the issue would be to also detect the add footer, but if I recall you 
can specify in dkim to sign only a certain length of the body and not the whole 
body. 

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