He's recommending you hide (redact) your account number because its associated with private info about yourself if someone were to able to use your account number to access personal/private info about you (e.g. real name, home address, capital info) or they may do worst such as cyber crime.
Thus, if you redact (hide) your account number from your screenshots...you're protecting yourself and it the forum owner Baron will not be mad at you for doing that. Thus, its not a violation of forum rules to post redacted screenshots of your broker trade execution platform.
If you still don't understand...pretend at the top of your broker trade execution platform instead of showing your account number...it shows your full name, country, city, home address, telephone number, name of your family members, education background, credit card numbers, passport, drivers license, photo etc...
I'm sure you would
redact (hide that info) if it was visible in your screenshots of your trade performance.
Remember this...the largest industry with Hacker problems is the financial industry. Don't make it easy for someone out there to gain access to personal/private information about you unless you're trying to get hacked.
There has been a few members here at this forum that have complained about being hacked. They too were members that use to show their account number in their broker trade execution platform many months earlier to their complaints.
wrbtrader