I felt this thread should be made, so I'll discuss the difference between the two:
Part of being a community really is helping eachother out, really. However, some things are definitely more harmful than helpful.
It really depends on the kind of criticism you're seeing.
Constructive criticism is the kind used to point out areas that might need improvement, to give helpful advice, or to suggest ways of improving
Destructive criticism often includes unhelpful advice (ie: saying something looks bad without giving any reason why), offensive comments, or discouragement of continued works.
When giving someone advice, you should use constructive criticism.
Giving someone destructive criticism is, on the whole, not appreciated in these forums.
Help build eachother up rather than discouraging or knocking eachother down
A second point I'd like to make is in respect another user's style/preference in method (This is mostly in response to anti-Minemator comments). You may (politely) suggest a different way to get from Point A (the beginning) to Point B (a finished product), and you may support your claim of how Method B may be more flexible or more efficient than Method A, but when it comes down to it, it's a creator's choice on what method they would like to use. As with criticism, one should not just say that a program "sucks" or tell a person to flat out stop using a certain program. One should suggest or offer advice but not demand.
I agree, it is important to understand that people will take your opinions seriously.
Making unhelpful and/or negative comments offends others.
If you don't have anything to say that is helpful, I recommend to not say anything.
People may not always think, 'oh someone said my creation is bad, is there something I could do to improve it?"
Often, this sort of sentiments is created, "oh that moderator says my build is bad...I'm pretty bad at this.."
This doesn't just apply to the forums/server, this applies to your real life.
If your friend/colleague made unhelpful comments about your creation you worked hard for, won't that make you feel down?
Thanks for the post Arc. Please be careful of what you say/write, everyone.
Don't blame this on you man its not your fault this happend. People just need to be more carefull of what they saying. You did nothing wrong.
I'm not. I'm actually somewhat honored. I was kinda taken aback when i saw this post, and when I read it in-depth, I got the feeling that i influenced this post. I was actually surprised I had that kind of influence on this part of the forum.