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Could anyone please explain the parts in bold?

1) My husband watches a lot of trashy TV at night—not that I don't have my guilty pleasures, too, mind you.


2) Moustaches were allowed, not that they did much for a few who grew them.
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Hasibrahmannot that ...

Probably the easiest paraphrase for the usage you've illustrated with your examples is

~ but don't think that what I just said means that ...


Wouldn't it be better if we did away with campaign finance limits? Not that I will ever be able to give anything approaching $2,300 to a candidate. ~
Wouldn't it be better if we did away with campaign finance limits? But don't think from that question that I will ever be able to give anything approaching $2,300 to a candidate.

CJ