[kjs3]

It's a embrace-extend-extiguish play like the old days. Add a 'feature' that doesn't technically break the rules (or only does a little), get your users used to it (by making it the default, opt-out, etc) and hope that your users will pressure people not using your product to move. "What do you mean you didn't see my email reaction? That's the best feature in the whole world. You should really switch to outlook, etc.". See: every M$-only feature in IE.

[dpark]

How is this argument not just “no one should ever implement new features”?

I don’t really care for the Outlook reactions and find them out of place, but this implementation doesn’t break anyone else. It’s also exactly how Apple implemented reactions being sent to SMS recipients.

Disclosure: I work at Microsoft.

[kjs3]

Yes, we got the "you're just a luddite that hates progress" sophistry from you guys in the IE days (and before). "We're doing the same thing as Apple" isn't a particularly persuasive counter. I always appreciated Balmer in that that he didn't waste time bullshitting anyone that he was trying to create walled gardens for M$ products by cooping standards.