I really feel both sides of this. On the one hand, I like customizing things, and I love to see users getting involved in platforms they love. On the other, I see how responsibly providing APIs is a big long-term burden that can prevent internal innovation.

I was talking a while back with some Mozilla people about the move from their legacy API [1] to WebExtensions [2]. It was a giant pain, but their old API exposed way too much surface area in ways that were too closely tied to the original implementation. The way I heard there were significant ongoing costs in trying to maintain the old API and support popular extensions while trying to improve the underlying tech and the user experience. So I get why Slack is very reluctant to expose API surface area, especially for the UI.

[1] https://developer.mozilla.org/en-US/docs/Archive/Add-ons/Leg...

[2] https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web...

That is because an API should express high-level concepts, not low-level implementation.

Just as the new WebExtensions API does. And as any hypothetical Slack API should.

In deprecating functionality necessary for the extensions that made Firefox worthwhile for me, though, the reasons to prefer it over other browsers evaporated.

Have you considered asking them if you could continue running your system if you agreed to add a permanent large banner at the bottom or top stating clearly that your system may break user experience?

I realize they are saying something about privacy, so it may be their position to argue against every system that does what your's does...

That’s a good point. I’ll def ask after I take it down and let them know. Thanks!