I walked into this thread expecting it to be full of some nice tributes to Jenna's time as Clara (as predominantly the thread about Karen leaving was a few years ago).
Instead I find a load of posts of wild over-reaction to Jenna admitting she's taken a few mementos from the set (FYI - actors do it fairly frequently, it's nothing new) rather than people reflecting on the fact she's been working hard on the show for pretty much three years now. That's a pretty disheartening reflection on this forum in my opinion.
For my part, I'm certainly going to miss Jenna when she bows out - it took me a while to really warm to Clara, in fact most of the way through the series she did with Matt Smith, but she's grown in stature as the episodes have progressed and last series she was truly impressive (and she's started this one the same way), and Clara has become one of my favourite companions, and her partnership with Capaldi one of my favourites even though Capaldi wouldn't be close to my favourite Doctor.