Little Bobby Tables we call him.

Mask slipped? The bot saw a person speak code and was like l, rips off mask Comrade!

I think there's a second mask. Who sends oops wrong person in the same text message?

Maybe it's an attempt to evade automated systems that check for spam.

Probably a basic way to evade spam detection. If you start sending the exact same message to 500 people, most chat services will shut that shit down in an instant. But if you send unique messages, it makes you look more like a real person, and the chat system may let it slide.

So that their fixed script isn't so predictable that we can just nuke them by looking for identical conversations.

I would say more likely to get around bot protection.

Could be to match the style of the target, to try and make the conversation feel more natural for them.

My guess would be the response text is passed through a rudimentary templating engine that looks for { and }. Somehow it must be processing the whole chat history. The templater fails at the unexpected braces in the code block and then just gives up (probably a try-catch ignores the error and sends the message anyway).

I don't think the code is doing anything, it looks like it might be the brackets.

That effectively the spam script has like a greedy template matcher that is trying to template the user message with the brackets and either (a) chokes on an exception so that the rest is spit out with no templating processor, or (b) completes so that it doesn't apply templating to the other side of the conversation.

So { a :'b'} might work instead.