Discussion on question by Konstantin Gerasimov: Should I keep using this little trick to filter out candidates?

i would not apply to your ad. Unless you send me an email writing "abracadabra". Otherwise, no deal. While I am joking, interviews are a 2 way street. Your strange request is a good pointer for me that job would not be a good fit for me. I think you have to distinguish if you want to hire people desperate for a job, or experienced and employed people.

How would you react if a great candidate buried a similar magic word in his resume and told you he was no longer interested because your reply didn't include it?

You may well have filtered out the good developers who read this "trick" and decided they wouldn't even bother applying to anyone employing this method.

It could honestly get interpreted as something expected not to be done, because a good developer does not give in to silly requests and is expected to push against unreasonable things. So it might have been a double edge sword. Also having this requirement, I personally would search for any editorial mistake such as space before a comma or other aesthetical flaws and happily not reply for expecting of others what you cannot deliver - major red flag. But that's me. Also asking for thoughts seems like off-topic - broad and opinion based. Yet, I replied in a comment, so...