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Telegram allows you to chat and send messages to yourself. The search is decent and searches through the rich text description of links you sent too (so you can look for the title of a YouTube video despite having only sent the link).

You can definitely chat with yourself in Messenger. (also Slack)

With conversations.im or other XMPP clients it is also possible to chat with yourself :-)

Messenger can. Telegram can. Slack can. Signal can. Whatsapp can.

You can send yourself messages with iMessage and have them sync to your computer, if you use an iPhone and Mac. If you don't, then of course this isn't much of a solution, but that's how many people solve it.

Slack and most XMPP clients can do this.