I wish to be able to do something like this:
After clicking that link, which opens the user's Bitcoin Core wallet, the user sees that message and can edit it freely, and then go through with the transaction. Now, the usual blockchain stuff happens, not storing that message in the blockchain. Considered "off far less importance" than the transaction, and to prevent abuse, this message flies around in the RAM of nodes on the Bitcoin network until I come back online and my wallet "receives"/sees the transaction, upon which point that message is fetched by my wallet and displayed to me in relation to the transaction, and then marked as "dropable" from the network.
That is, the blockchain does not store this message, and if I'm offline for longer than, let's say, a few weeks or so, I never receive the message. It doesn't "fly around" forever; it's merely a very useful extra feature for people who are online reasonably often, as I would be if I'm accepting donations/payments and want to know what exactly people are donating/paying for.
Having a "dynamic" website with a live database and dispensing unique receive addresses is simply not practical for a lot of people and situations. Even though I know how to do this technically, and have done it in the past, it's a major PITA as well as a massive headache of maintenance compared to a more "static" website which is generated as HTML files and uploaded in bursts. The latter is far more secure and thus desirable for me, and that's why this would be a great thing to me.
I assume that it doesn't exist, or if it does, it doesn't have support, but it would be really cool if it did.