(Disclaimer; for ease of writing, when using the term Superhero, I am also including Anti-Heroes and Villains)
1) You start using Superheroes as your example for everything during conversations.
Friend: ... So then I saw this poor guy trip over his cane. I know I should have helped him, but all I could do was laugh.
You: I know what you mean! I was reading this comic the other day and Deadpool saw Daredevil trip and fall on his face, I laughed so hard.
2) The walls are steadily becoming less visible, as more and more Superhero related things cover them. (Or, you completely theme your space.)
At one point, your room used to have walls that were painted a delightfully safe taupe color. Now you have hand-painted wall murals, comic book wallpaper, posters, and shelves covering every inch. There isn't a single place you can look that isn't covered in geek or nerd heaven... Oh wait! The ceiling!
3) An intense sensation of euphoria or elation comes over you, just by being near your "collection."
Lifting the lid on the box you store your comic books in, you graze your fingertips over the crisp edges of their sleeves. Knowing that these babies are all yours sends shivers up your spine, and you return the affection you feel by perfectly (and lovingly) organizing them.
4) Not only are you aware of the slightest variance between a comic book and its movie or TV counterpart, but how the canon changes to fit the script.
You may have felt betrayed in some ways, that David Ayer paid no attention to which years of comic books he drew his character models from. Why does Harley Quinn look like she's from Arkham Asylum or Regime, yet The Joker is clearly a mix between The Killing Joke and Endgame?
5) You cosplay your favorite characters regularly, and get irritated by people who half-ass their outfits. Your costume couldn't be any less than set-quality or you would hate it.
Poised with your finger over your mouse button, you prepare to bid on an actual piece of a costume from the actual TV show. Who cares that you just spent $200 making bracers that are nearly identical; these are the REAL ones!
6) Taking up archery, learning the bo staff, or sword-play is something you have either seriously considered doing (or did do).
There would be no better feeling in the world for you than stepping into the shoes of your hero. The draw of the bow, the twirl of the staff, or the sound of swords slicing through the air fill your imagination.
7) The local comic book or collectibles store is familiar with the timing of your visits, knows your name, and what you will buy.
When you walk through those doors, and the smell of fresh comic books hits your nose, you feel like you've come home; the bright colors instantly make you feel happy, even on your worst day. You probably consider the staff your friends, even though you have never seen them outside of the store.
(Bonus points if something new comes in and they put one aside for you knowing you don't have it and will want it.)
8) Your animals are named after your favorite characters; because you either thought it was cool, or needed their name in your life.
Calling out for Loki, Flash, or Captain Cold countless times throughout the day is the best thing in the world. They might even have little costumes or accessories to match their namesakes, because you think it's awesome.
9) Friends and family who don't understand your hobby have made themselves strangers. The increased isolation, or the death of your social life, has cause you to cling even harder to your heroes.
No one understands why you love what you do, or why Superheroes inspire you to be a better version of yourself. If only people could see that by setting your standards so high, you make your potential endless!
10) Vigilantism or criminal activity is something you have actually thought about.
The world needs Superheroes! Maybe it would be a better place with someone to take care of all the criminals that plague your city. But on the other hand, being a Super-Villain and just taking everything you want, sounds appealing as well. For those of you who can't choose sides, you have probably considered becoming a hacker like Barbara Gordon, Felicity Smoak, or Noah Kuttler.
11) You have made the decision that should you have a partner, and they make you choose between them or the lifestyle you have built around Superheroes, you wouldn't pick them.
While most relationships end in failure, your love of comic books and Superheroes will live on forever; and unlike the real world, they will never break your heart, cheat on you or leave you. You know that even if the current writers kill off your favorite character, another canon will just bring them back! Plus true love is about acceptance and should be unconditional, and that includes loving what matters most to you!