Update 'Double link' description

I find a few ppl (including me) were a bit confused to the meaning of "Double link". https://gitlab.slack.com/archives/C0AR2KW4B/p1475502871001568

So after @tayloramurphy explained it to me I feel rewording would be nice: https://gitlab.slack.com/archives/C0AR2KW4B/p1526049137000252?thread_ts=1526022641.000179&cid=C0AR2KW4B

As a side note, "Double link issues..." was originally worded "Double check issues..." 5bb3d7b7