[onetoo]

Not just private chat, almost any chat channel can be used[1]. It's quite common for certain addons to quietly share their versions upon e.g. joining a group, so that you get a notification if a new version is out. It's a bit of a longer explanation, but another fun example of out-of-band privileged information in World of Warcraft:

The "fight" between Blizzard's boss design and addon creators trivializing said encounters is long and not worth going deeply into. But, for example, if the strategy of a boss is "if you get a glowing glyph over your head, run over there and stand in a square formation with the other guys with glowing glyphs", an addon could use hard-to-ignore sounds and visuals to tell you that a) you have to run now, and b) exactly which corner of the square formation to run to.

I believe that in the latest raid, the developers tried restricted certain information from the API (e.g. "there is a glyph over the player's head") in an attempt to reduce that kind of strategy automation. The players then proceeded to manually feed this information (e.g. "i have a glyph over my head") into their addons using buttons mapped to API calls like this, allowing for partial automation (e.g. "your corner in the formation is top-left"). This stirred quite the drama, but the that's besides the point.

[1] https://wowpedia.fandom.com/wiki/API_C_ChatInfo.SendAddonMes...