It helps that Zoho's main competitor is GSuite. That's what a lot of us are comparing them against and it's just not very difficult to beat Google's "non-existent unless you spend $millions on ads" support, they could literally have a cat answer support and it'd be an improvement. Anyone who has had to deal with trying and failing to get anything answered by Google and then tried the same with Zoho will have something good to say about them regardless of their product overall.
Zoho's products are also a bit more "traditional" in the way that people on HN tend to enjoy. Their UIs, configuration, features and all aren't very 2024 glittery but they're good for getting shit done and setting stuff up yourself.
And then they're also cheap which HN tends to be sensitive to, here you see many contemplate self-hosting things every time a SaaS increases their pricing. Or write about moving back from Big Cloud to bare metal or Hetzner and co. to save $.
However, while I have not made use of their paid services (as I use it just for personal use), I have referred clients before to Zoho when I have been working on their websites.
I've also made use of their invoice software free of charge to generate a couple invoices and have been quite pleased with that as well.
Sometimes when companies are fair to their customers either via pricing or business practices, it results in people being much more willing to go out of their way to say good things about the company. It would be insane for me to be negative against a company that has provided me a good product for free for years upon years. There aren't even ads.