Forbes – Vaclav Vincalek Forbes Councils Member Slack is now worth about $23 billion after their amazingly successful listing on the New York Stock Exchange.  About five minutes after their triumph, it would be funny at best, or arrogant at worst, for me to write communication platforms like Slack an open letter offering advice — so I’ll go with “funny.” Consider this friendly advice from a Slack user who is also a tech CEO with decades of experience implementing communication and collaboration solutions. To survive,…