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Pseudonyms or real names
(geekfeminismdotorg.wordpress.com)
Even if you use your real name, the online persona remains an artificial presentation and using a handle for that reduces the likelyhood that people confuse it with the actual person.
In a sense, a handle is like a core part of a hacker's personal brand.
A place for discussing cybersecurity, but also for discussing hacker culture. Hacktivism, cyberfeminism, crypto-anarchism, internet vigilantism, and so forth.