FYI: You can still close the tab, just not by clicking the (no longer visible) X. This may not fit your use case, but then again it might (I can't remember the last time I closed a tab by clicking instead of with ctrl+w).
he is saying that he wishing pinning tabs _prevented_ the tab from being closed (as opera does). I have closed pinned tabs my mistake before (ctrl+w too many times) and I agree.