I realized that if kpart-webkit is not installed konqueror uses khtml and the issue is not present, but if it is installed and webkit is used in konqueror, then the effect occurs in konqueror as jajaX mentioned above
In rekonq the issue always happens, irrespective of kpart-webkit, when mozilla-libreoffice is installed
So it seems that is the combination of libkdewebkit5 or libqtwebkit4, and mozilla-libreoffice what makes the issue to appear in rekonq (and in konqueror if webkit is used through kpart-webkit)
I realized that if kpart-webkit is not installed konqueror uses khtml and the issue is not present, but if it is installed and webkit is used in konqueror, then the effect occurs in konqueror as jajaX mentioned above
In rekonq the issue always happens, irrespective of kpart-webkit, when mozilla-libreoffice is installed
So it seems that is the combination of libkdewebkit5 or libqtwebkit4, and mozilla-libreoffice what makes the issue to appear in rekonq (and in konqueror if webkit is used through kpart-webkit)