Per Andre's instructions, I'm creating a new ticket. Double thanking for the same edit is still allowed and it should not be. I should be able to see which revisions I've already thanked for in page histories regardless of session.
I double thanked Scott Martin for https://en.wikipedia.org/w/index.php?title=User_talk:Technical_13&diff=594071365&oldid=594071255 as can be seen in the thank log https://en.wikipedia.org/w/index.php?title=Special:Log&type=&user=Technical_13&page=User%3AScott_Martin&tagfilter=&hide_patrol_log=1&hide_review_log=1&hide_thanks_log=0 and he has confirmed that he was thanked twice for the same revision "I got a notification on the 22nd and then again today." ([[Bugzilla:46690#c11]])