Yes, removing
https://bitcointalk.org is not affecting it being a valid URL but when I go again for editing the post, I do see
https://bitcointalk.org is getting populated automatically.
So, copying the URLs part into some other notepad temporarily (without
https://bitcointalk.org) and pasting them back into the post just before the LAST edit may serve its purposes

.
Until theymos' post, I omitted the "https://"-part from
my mobile signature to make it shorter, but indeed, it always reappeared when editing the signature (after which I hits the 4000 character limit). I use the
Archival board to store the shortest version within code-tags.