Such questions are discussed whenever developers and users of DFT meet -in conferences and workshops, during coffee breaks and over dinners. We do not expect short, clear answers to such questions but the discussions and conversations they give rise to are often informative and entertaining -and different to discussions in publications and presentations. We learn about new ideas and developments and about failed attempts -a casual remark may trigger new research or lead to new collaborations. These discussions are an important reason for travelling to conferences and something we have missed during the pandemic.