Hey, that is an interesting issue.
I may have found a solution. But I have only tested it on the current version. Try it for yourself. Instead of just having a cmd-block doing /say Hello World you can place down an armorstand with a specific name.
Give yourself a named armorstand.
/give EiTiRu minecraft:armor_stand[minecraft:custom_name=Michael].
And than run this command inside the cmd-block:
execute as @e[type=armor_stand,name=Michael] run say Hello World
It should read in chat as follows: [Michael] Hello World
I hope this helped. If this doesn't work please report back, I may have another idea.