[LukeShu]

Often reddit threads read more respectful after-the-fact; the less respectful comments either get downvoted enough that they aren't displayed unless you look for them, or are moderated away. Often they are much harsher early in the thread. I'm not sure if that ways the case here, but it is common enough that I wouldn't doubt it.

[mystrman111]

When comments are removed by mods on Reddit, they're replaced with the text "[REMOVED]", which doesn't appear once in the referenced thread (insults would not be removed in the first place though, they break no /r/webdev rules). And you can scroll to the bottom of the thread to see all the downvoted comments, none of which are are condescending towards Mark. So no, that isn't the case here.

[pwdisswordfish]

I believe the [removed] only appears in place of comments with replies that have not been deleted.

Though yeah, that still makes it rather implausible.

[LukeShu]

In the default sort mode ("best"), sufficiently downvoted comments won't be displayed at all, even if you do scroll all the way to the bottom.