All versions are the latest. No, I have not tried to investigate, I just spotted it in error_log and it makes false alarms for me. Investigation may take a day, depending on the number of plugins, but the message is so clear, that if you simply put ‘if(isset())’ in the place with proper handling, it will be gone regardless. What difference does it make, which plugin is in conflict if any, the fix you would do is the same: just more clean code.
While working on other plugin, I came across that this message appears when current_user_can() is called from within ‘plugins_loaded’ action. If user authentication is not expected at this point, then this proves that it is not BuddyPress problem.
Which action, as early as possible, would you recommend to use expecting current_user_can() to work properly?
You got me, Henry! No, it does not. I now have been turning on/off other plugins and I got a combination: “Twenty Fifteen”, BuddyPress and “Favicon by RealFaviconGenerator”. If I turn off either BuddyPress or Favicon, the message disappear. Do you wish me to report it to Favicon, or would you look first what exactly is wrong?
