Why a question is not shown among linked questions?

This comment links to the question: On the inclusion of pages-of-text-as-images in questions

However if you look at the linked questions of that question, it is not shown there: homework questions, again

Why did it happen here? Does it have something to do with the fact that this link was originally posted in a comment to an answer, which is now deleted? Or perhaps with the fact that I have deleted a comment containing the link, and then posted a new comment? (The old one did not contain ping.)

• Feb 10 '14 at 11:39
• The question linked in this answer was shown only after it was added once more in a comment. (Perhaps the reason there might be migration?) Mar 11 '14 at 7:11
• Another example: math.stackexchange.com/questions/743257/… (This time the reason might be that it was migrated from meta.) Apr 7 '14 at 8:47