I can't reproduce any of it on Win-10 with Sigil 0.9.7 either.
Back on Kubuntu, shift-click works as expected in code view, and ctl-click works in the clip editor, for example, and I haven't knowingly re-assigned the ctl key in preferences (if in fact you could).
I think it's been happening on kubuntu with various Qt 5.x versions, and maybe even 4.x as well, but I won't swear to it now.
Not much help, eh?
Albert