That's about the level of evidence that your specific user account offers to you about whether phone verification is a thing their anti-spam algorithms can trigger...
https://support.discord.com/hc/en-us/articles/6181726888215-...
> You'll be required to register a phone number to your Discord account in order to continue the use of it.
The following is worded in such a way that it very much reads that you're saying it doesn't happen...
>When other people say that something happens to them, why should I simply take them at their word when it contradicts the evidence actually available to me?
You've very clearly said that if something hasn't happened to you, you're not likely to believe someone when they tell you it's happened to them. Further...
>You seemed to be implying that it will always happen, or commonly happen...
... there was no implication. The comment you initially responded to clearly stated specific instances that will trigger the phone number requirement, the same instances that are very clearly stated by Discord[1] itself.
And I'm saying that I've personally been (as far as I can tell) in some of the situations described without encountering such requirement, therefore "will" is hyperbolic.
It especially doesn't make sense to me that there would be a flag for "joining too many servers" because they put a hard cap on that anyway. And indeed, the support article says that this triggers for joining too many servers in a short period of time.
I would think that the appropriate response is to show more concrete evidence; in this case that could be the related policy, for example.
More to the point, the post I responded to says "It happens if...". I think that can reasonably be understood as logical implication. If it was meant to mean "it can happen if..." then I genuinely don't understand why or how I was supposed to come to that interpretation.
Especially with the bit about servers that require it. It read to me like the claim was that entering such a server would automatically flag your entire account. I know that not to be the case from my own experience.