Before I finish reading this article:
There is nothing more than annoying than using a site which hides dates, and this even includes my own sites before I get around to implementing a feature to show dates on them.
And I have considered hiding them simply to simplify the UI a bit, just so that I don't have as much superfluous junk no cares about.
If it's a blog, then I generally won't look down on it because it's blog posts were a long time ago, in truth, a lot of important posts on blogs worth reading were probably written about a decade ago, so this is nothing unusual to me.
I probably wouldn't bother subscribing to it, if I don't think it's worth the time to do so, I hate subscriptions with a passion. But, that wouldn't stop me going through it to see what they have after landing on something interesting. Content is king.
Also, don't worry about a blog being dead for weeks or months. This is actually fairly normal for a blog.
After reading it:
An interesting perspective, but I think you're slightly missing the point here. Hiding dates is more annoying than anything else. It reeks of either a smart ass who is too smart to put in basic information for me to look at or an idiot.
I wouldn't even remotely consider that someone is doing it for SEO, but that they're being extremely, extremely lazy and cutting corners.
Also, I deliberately filter dates in search results, that is a thing on Google. Otherwise, you end up in a situation where you get a lot of obsolete articles from a decade ago teaching me the wrong thing.
A "genius" who is actually inside the right time window but thinks a year old article is "too old" would end up getting excluded from my query, simply for doing that.
All in all, trying to screw with things like this is more likely to backfire badly on you than to have any real tangible benefit. Not to smack you down here, but that would basically be my immediate gut reaction to a site trying to pull this.
As always, the way is to just pump out more quality content, market your site, etc.
What search engines and anyone really cares about is more content more than anything.
Activity might matter, if you run a forum, but people are going to be driven up the wall before long without dates on posts.