The rationale was simple:
We were trying to be funny and reflect our company culture ...
And that is typically the rationale. It's where it all started. In a distant past, you may have posted a job listing for a software "professional." But market demand for talent became increasingly competitive and employers sought means of distinguishing themselves to candidates. A perfectly natural response was to make the listing read differently so that it looked more desirable. Perhaps instead of listing for a "professional" you might list for an "expert" (because, I suppose, professionalism does not necessitate expertise).
But now "expert" became the norm. So someone wrote a listing for a "master."
Then a "guru." Then a "ninja", then "rockstar," then "virtuoso," then "wizard," and so on.
When I saw the use of "unicorn" this morning, I grimaced. What may have started off as an earnest, endearing, and yes — even playful — culture exhibiting signal to applicants has now become a full blown lingustic arms race, and this guy just launched a nuke.
To be clear, I don't have an inherent problem with this practice. I'm not mad at anyone, and this trick isn't objectively wrong in any way. The technique is used to cause applicants to self-select. If I'm a professional programmer (I am) and see a hundred listings for a "professional" and one for an "expert," guess what? That one will stick out, and I'll probably click on it first. Doesn't have any impact on what I do next, but you're at least likely to get a page view from me.
But if I see a hundred listings for a "professional" and one for a "unicorn" you can bet your bottom dollar that I will never visit the link. All business tactics reach a point of diminishing returns. A plateau of efficacy. But some business tactics can be much, much worse; going too far can cause you significant harm and move the needle in the wrong direction.
I will happily self-select away from the unicorn listing. Not because get-off-my-lawn, but because it signals to me desperation and a lack of creativity. When you're looking to fill a role and you want to harness self-selection in an intentional way, you must consider the power you wield as a result of the words you choose; don't just do the standard thing to a greater extreme. More checkboxes don't close sales, the reasoning behind them does.
Is this grammatical Feats of Strength actually sending the message you intended? Are you causing the correct self-selection to happen?
As an industry, have we really thought this through?