In previous versions of Webkit every time I reloaded the page I would get a dashed line and the console would not clear. This was somewhat useful but for certain scenarios, like when debugging page load issues, it can get very cluttered. In the current Safari 9 beta there is the reverse behavior, either navigating away from the page or reloading the page is clearing the console.
I agree clearing should be the default behavior, but having and option to preserve the logs is specially useful when navigating away from the page and analyzing console.log messages that are happening on the click handlers and onBeforeUnload handlers when present.
This is sometimes also relevant for network messages. Some libraries will fire a network request (user metric libraries, for instance) before letting the user navigate away. In those scenarios I faced very hard to debug problems with Safari, specially when debugging Safari over USB to get actual device results. Would be very helpful to have the Safari WebInspector to hold this data and it's visualizations in memory as an option.
Right-click on the messages area in the console and you can enable the old behavior.
Oh... that just happened.
Sorry, I never found this one. Should I create a separate one for network? I would say it's less important, but it's sometimes useful to get the whole lifecycle of navigation through some different pages in traditional websites (not SPA).