hmm odd issue as links should be auto embeded no matter how you paste them, some how the link is being put in the code in " " and that's why it is shown as text and not a link, now if that is caused by the browser or the editor i don't know with out spending time reading the coding, also is it just HTTPS links doing this or is it HTTP ones too?
lets see what this does:
"https://linustechtips.com/"
"http://google.com/"
https://linustechtips.com/
http://google.com/
EDIT:
well they all work so it is passing the text written in the editor correctly, its almost as if under certain situation it thinks the link is just text but that shouldnt be possible no matter the format, unless something in the code of the forums is telling the browser not to show the link, the same way the code tags work.
its not browser specific, as i can see the broken links on my screen too.
FYI - i do see 7 warnings and 4 errors in the code for the site when i debug the code as well which wont help matters.