While it is possible to prevent accidentally closing the browser with a ⌘Q command (in Preferences > Show warning before quitting with ⌘Q), it is not possible to do the same with pinned tabs (there is no Preferences setting “Show warning before closing pinned tabs with⌘W”). This would be particularly helpful with mail programs, where you think you are closing a message, but are really closing the entire tab.
The process is too slow:
Option 1 (via mouse): Menu > People > Select Person
Option 2 (via mouse): Toolbar > Click on Person icon > Click on other Person icon in submenu