Two articles from Planet Debian on the same subject, which has been plaguing me as well. There might just be a solution.
Debian has generally always had, as a rule, “sane defaults” and “no surprises”. This was completely shattered for me when Vim decided to hijack the mouse from my terminal and break all copy/paste functionality. This has occured since the release of Debian 9.
The solution might be installing in .vimrc:
if !has("gui_running") set mouse= endif