I suspect that the word would not be acceptable in a signature.

Yes it is the term used to describe a female dog, however, it is also a profanity meant in a derogatory sense. And when people call someone a "Bitch", it's meant in a derogatory sense.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi