What does it mean?

Reserved for a giveaway later.

Obligatory SteamGifters' most wishlisted Bad Rats giveaway

They don't want to have 2827814 messages popping up of people thanking them. Read the description before posting. If they blacklisted you, must be because of a different reason. Maybe your ratio perhaps?

Sounds like the person was just being a dick IMHO.

You didn't read it wrong but I think he/she was looking for a personalized thank you, rather than the generic "thanks".

People like that aren't worth your time in the long run, just move on, there are thousands of other, decent members on this site you can interact with. :D

Some people will blacklist you if you join a GA (or especially win a GA) without commenting. Some will blacklist you if you comment in a generic way instead of saying something thoughtful and relevant. It really depends on the person, and sometimes on the GA itself. The comment you quoted was obviously meant to be sarcastic, but I don't know the circumstances of you being blacklisted - you'd have to ask that person, if they'll answer you.

Best advice I've accumulated about this - if a GA has specific instructions, read them and follow them. If not, either say something relevant to the GA or the person, or don't say anything at all. But always thanks the person after you win.

those messages are usually to blacklist people using bots to enter giveaways, or scripts that add a JOIN button so you don't even need to enter the GA page (missing the description).

if you didn't say thanks/thx, then maybe it was a mistake? or the creator also blacklisted everyone that didn't reply?

The obligatory giveaway is now there.

No, you've read right, they should have been more specific.
Don't worry about it:)

At least I did not understand it wrong...

88BCE-JVKK9-KFG8K

awww. ;-;

Let it be. Some people thrive in any pathetic crumb of authority they can get.