I summoned Armor stand named Coal (summon minecraft:armor_stand ~ ~ ~ {CustomName:"\"Coal\"", CustomNameVisible:1})
Then i tried to kill it {/kill @e[type=armor_stand, nbt={CustomName:"Coal"}] but i got "No entity was found" message.
I tried it also with pig and it doesnt work too.
Names are components (MC-123807); you're using a component when creating the entity but not testing for it.
should work, or
@e[name="Coal"]should also work.