Bitcoin is not a messaging system.
However, the OP_RETURN code was added so that some data could be embedded in the transaction outputs if someone wants to.
None of the standard wallets provide a user interface for embedding data, nor do they provide any method for viewing any embedded data. This is because Bitcoin is not a messaging system.
However, there are services that will charge you a fee and will create transactions with embedded data for you. Most of those services will also display that data on their website.
Yes, I get that Bitcoin is not a messaging system. I was asking out of curiosity, and also to maybe in the future mark certain addresses as proof for tax reasons. It's not good to spam and congest the network, I know.
Which services would do that, can you name some?
And btw, I applaud you for restlessly answer questions on this forum and educating people. Bitcoin needs people like you, so thanks!