ich_iel

Yes, If the attacker doesn't know if you used a special char or not, it does not matter if you do...

Es wird noch schlimmer: dA%6f}y bei freier Wahl des Passworts ist ein besseres Passwort als dA%6f}y, wenn du Sonderzeichen, Zahlen, Groß- und Kleinschreibung verwenden must...

https://xkcd.com/936

Basically if B is the number of possible symbols and n the length of your password then the number of possible passwords is B^n

This number grows faster for increasing n than for increasing B. So even passwords on only two symbols will be more secure than passwords containing any possible unicode symbol - as long as they are long enough.

In the case where an attacker doesn't even know whether you are using fewer possible symbols or not the number n is even more important. Also if people are forced to use certain characters they tend to use shorter passwords just to be able to memorize them. However if an attacker correctly assumes that you are only using lower case letters he will still have an easier time guessing your pwd just because you followed a strategy.

Humans are generally bad at thinking about randomness. Most would assume that AAAAAA is a less random phrase than €jK6%g but they are equally likely and therefore equally safe - if your enemy isn't also a human / knows that you are one and tries AAAAAA first before testing random phrases.