1. /summon minecraft:marker ~ ~ ~ {data:{nbt:["\""]}}
(marker summoned)
2. /data get entity @e[type=minecraft:marker,limit=1]
(nbt is correct)
3. /tellraw @a

{"nbt":"data.nbt","entity":"@e[type=minecraft:marker]","interpret":true}

(bug: empty line printed)

['"'], ["\"text\""], ["

{\"text\":\"something\"}

"] prints empty line too