Let's not give Reddit's management too much credit. They've lit a decade's worth of investor and advertiser money on fire and have precious little to show for it. Their recent moves seem less like calculated business decisions and more like desperate scrambles to make the site appealing to public investors on very short notice.

Yes, as long as the business communicates and executes well and makes the value proposition of the choice clear to their customers, either works. Being backwards-compatible to the beginning of time is not the only choice. My experience in the industry, however, is that most organizations cling to never breaking compatibility, under the flawed belief that it's always simpler or cheaper than planned migrations.

You're right! It's been a long time. There was a 68K to PowerPC, then later Power to Intel, and now Intel to arm64.

They are, but in my experience businesses will tend towards backwards compatibility without adequately weighing the costs of one versus the other. Cargo cult compatibility, so to speak.