[thelegendaryof]

I totaly agree that a proper solution would be a communication API. However they even removed sending Chat-Messages programmatically from addons in addition to limiting the BrowserControl to preset internal pages. That 's only sh*t for legit Addon-Developers as every Mother and their Kid can write an simple AutoIT-Script that just does that chat-spamming and even more (and it 's not even like professional Goldsellers are using the API for that to begin with).

Meaning I wouldn't hold my breath for that for a long time (however wonders might happen - seeing that they didn't even respond in 2 months to the request ESOUI made for releasing the official UI here makes me rather think the opposite).

However sending hidden Chat-Messages would be another way - BUT - if a user doesn't have that Addon it would be even more intruding as they get spammed by messages they don't want to see. At least in the Guild Notice no one is getting any Notification of it.

Technically both can't be spammed as they have a limit just how much you can spam/send before you get kicked.
So of course it would only have a technically AND ethically limited usage - that 's for sure.