It doesn't matter if you perceive it to be stupid or not. I've done the math and the ending of letting everybody know how I did it and what software I did it with will not be good. My site wouldn't be unique anymore.
Moreover, Joomla has like 2k additional themes, MemHT got like 2 good ones so it's a different thing. Even though I've customized the theme pretty much, people would still see similarity to my site. What happens when 10 other people uses this and come to my site? Oh it's just one of those 10 other portal sites.

I'm not doing it to be haughty, I just want to protect my business as far as I could.

I'm probably opening up a new site related to web development later on, where copyright text will stay as it's a much more open and wide topic.

Tibia is something small, yet a lot of people are in need of such site, none even really came up with the portal idea before, they just go with vB.

Everyone is free to do whatever he wants + Don't judge and you'll not be judged.