(I don’t think the standard bug report layout will work for this post, sorry.)
All testing done with version 0.12189.
I decided to test how every move interacts with itself (in a mirror match) when used on the same frame. While in most situations the results are expected, there are also many situations where results occur that are either asymmetrical (which implies port priority, a very unfair mechanic), or otherwise unexpected (such as both players being hit without taking damage). Some of these might be intentional, while others are likely bugs, so I thought I would share all of my findings here.
Ensuring moves came out on the same frame was done by pausing the game, holding the button for both players, and then un-pausing the game. Jumps were also started on the same frame for aerial attacks. Moves that are executed when the player releases the button were done by starting the charging period on the same frame, and then pausing and unpausing the game to release them on the same frame. I have since gone through and tested problematic moves using the frame-step option. Thanks Bomber678 for letting me know about that! All moves were done at point-blank (unless otherwise specified), including projectiles. Asymmetrical results have been tested once with each player on the left and once with each on the right.
Unexpected results are bolded.
GRAVE (N means without Wind Summon, EX means during Wind Summon)
Both players hit for 1 damage: Knifehand, Double Palm, Sweep, Jump Kick, Lightning Cloud (Small N, Small EX, Big EX), Hurricane (N, EX), Sword Slice
Only Player 2 is hit for 1 damage: Lightning Cloud (Big N)
Both attacks miss: Dragonheart
JAINA
Both players hit for 1 damage: Low Kick, Knee, Roundhouse, Divekick, Flame Arrow (Lv 1, Lv 2, Lv 3), Air Flame Arrow, Dragonheart^
Projectiles clash: Sky Arrow, Rain of Fire
Both players hit for 0 damage: Red Dragon
^ Plus the damage from use, for a total of 2 damage.
GEIGER
Both players hit for 1 damage: Low Punch, Backhand, Step Kick, Aerial Kick, Flash Gear, Drop Gear, Cycloid Revolution
Only Player 2 is hit for 1 damage: Time Spiral (Normal, Delayed)
ARGAGARG
Both players hit for 1 damage: Staff Strike, Stretchy Punch, Stretchy Upward Punch, Stretchy Diagonal Punch^, Staff Drill, Rushing River (Neutral, Forwards)
Both attacks miss: Sparkling Bubble (Normal)
Both players hit for 0 damage: Flying Fish (Blue)
Both players poisoned: Flying Fish (Purple)
Both players pushed back: Rushing River (No Fish)
Only Player 2 is hit for 1 damage: Sparkling Bubble (Bubble Shield)^
Both attacks are blocked: Rushing River (Backwards)
^ Player 2 is knocked to the right regardless of which side they started on.
SETSUKI
Both players hit for 1 damage: Knee, Elbow, Double Palm, Slide, Divekick (Neutral, Backwards), Ninjaport (Kick), Kunai (Neutral, Backwards), Flying Fox
Both attacks miss: Ninjaport (Teleport, Throw), Starlight Tumbler, Esper Dash
VALERIE
Both players hit for 1 damage: Mid Stroke (1)^, Low Stroke, Double Kick (Hit 1, Hit 2), Aerial Swipe (1, 2), Three Colors (1, 2^^,3 Neutral^^), Cross Stroke^^^, Rainbow Stroke, Flying Rainbow Stroke, Rainbow Disc
Both attacks miss: Three Colors (3 Forwards)^^
Both players hit for 0 damage: Chromatic Orb
^ I was unable to test Mid Stroke 2 because it has the same reach as Mid Stroke 1 (as far as I can tell), so Valerie would always get hit before she could perform Mid Stroke 2.
^^ Buffering inputs using frame-step doesn’t work for this move, so results may be inaccurate.
^^^ Tested at a distance; misses at point blank. Player 2 is knocked towards Player 1.
ROOK
Both players hit for 1 damage: Sweep, Kick (Hit 1, Hit 2), Thunderclap, Splash, Rock Punch, Landslide^, Vine Spiral, Ground Pound (Direct), Head Crush
Player on the left side throws the other: Checkmate Buster
Both attacks miss: Ground Pound (Knockdown)^^, Ultimate Checkmate Buster
^ Neither player is knocked back. (Causes a visual bug that makes Rook clip into his opponent until hit by another move.)
^^ Tested at a distance; unable to be tested at point blank.
MIDORI
Both players hit for 1 damage: Chop, Flurry Punches^, Two-Hit Strike (Hit 1, Hit 2), Sweep, Jump Kick, Floating Axe Kick (Neutral, Forwards, Backwards), Flying Kick, Air Flying Kick, Butt Slam, Bow, Take Flight^, Bite, Tail Sweep, Claw Swipe (Hit 1, Hit 2), Dragon Torpedo, Air Dragon Torpedo
Both attacks miss: Acid Spit^, Dragon Buster^^
Player 1 throws Player 2: Talon Swoop
^ Buffering inputs using frame-step doesn’t work for this move, so results may be inaccurate.
^^ (Causes a visual bug that makes Midori clip into his opponent until hit by another move, even if he reverts to Human Form.)
LUM
Both players hit for 1 damage: Upward Claw, Long Punch, Claw Sweep, Giant Aerial Kick, Panda Ball, Polar Cartwheel, Item Toss (Cloud^, Coin), Melon Toss, Slot of Items, Roll the Dice^^
Both players hit for 0 damage: Item Toss (Mini-Rook)
Each player takes a random amount of damage from 1 to 3: Item Toss (Fireworks)
Player 1 takes 2 damage and Player 2 takes 1 damage: Item Toss (Bomb)
Projectiles clash: Item Toss (Mini-Lum)
^ Tested at a distance; misses at point blank.
^^ Tested by hitting the dice at point blank, which also hits the other player, dealing 2 damage total.
DEGREY
Both players hit for 1 damage: Punch, Punch of Justice^, Overhead Kick, Ground Pound, Two-Fisted Punch, Aerial Punch, Counter-Point Step (A, C), Flying Kick (1, 2^), Final Arbiter
Both players hit for 2 damage: Counter-Point Step (B)^
Both players hit for 0 damage: Ghost, Air Ghost
^ Buffering inputs using frame-step doesn’t work for this move, so results may be inaccurate.
Normal throws seem to randomly decide which player succeeds at throwing. Argagarg is an exception: both throws miss.