I reckon this happens sometimes while adding a link using the "insert hyperlink" tool (either by clicking the button or pressing Ctrl+L) instead of using Markdown.
The input box contains https:// (which is selected) by default
(and I believe it used to have http:// by default previously). So usually while pasting the link, it overwrites the https:// with ...
The problem seems to be caused by copying a link with a preceding space into the Insert Hyperlink dialog. The software adds http:// in front of it and a broken link starting with http://%20https:// is born.
See What causes “http://%20https://” links to be made? on Meta.SE for details.
Treat these answers as if version-specific1. For example, we don't want to edit answers for 13.04 release to add information for 18.04 release ( unless it's absolutely necessary and relevant ). Same approach applies here: if the answer relied on Software Center specifically, editing the links out of the answer affects the original intent of the poster. As ...
I'd say it depends on the question.
If it is still current it should be fixed.
I would rather see someone do this directly on the database instead of editing every question manually. Try not to flood the frontpage while editting. If there is one thing that makes me leave AU for a day it is seeing 20 topics on the FP I don't want to click on.