[pvg]

You'd have to take out spam account creation which is a more likely explanation for much of these spikes. There's no corresponding increase in submissions or comments so these big increases in users don't appear to correspond to matching increases in other visible activity.

I looked at a related metric recently - unique users/N comments (i.e. how many unique users per, say, 100k consecutive comments). This number hasn't changed at all for many years.

[Karrot_Kream]

What makes you think spam account creation is up and what changed in the last 2 years that made spam accounts so much more easily createable?

Comment counts haven't changed but text post creation absolutely has. Given that no more stories are being flagged than usual, in fact if you amortize this over new user counts a lot less per user, I'm going to say that it's genuinely new text accounts that want to engage with HN by making text posts.

[pvg]

I think it's the other way round - what makes you think these vertical temporary spikes of account creation can possibly be organic growth? Even viral growth doesn't look like that and, again, it's not reflected in the normal activity of the site. Creating accounts in bulk has always been trivial, there was a spam post with 600 upvotes just yesterday.

As to the text posts, I'm not sure I understand its relationship to your original claim, that is an odd jump but it doesn't sound all that difficult to look into, without that we'd both be mostly guessing (my guess is still likely spam but I have no idea). Unless you already have?

Edit: I tweaked the query slightly and I haven't looked into the content but that kinda looks like spam to me? I.e. the number of nondead text stories hasn't changed in years. Spamdetection kills a lot of stuff as you can check for yourself by browsing /newest

https://play.clickhouse.com/play?user=play#U0VMRUNUCiAgICBDT...

[pvg]

And an example of a current text posting spammer: https://news.ycombinator.com/submitted?id=lilysmith3311