I think you misunderstand what the poster said about "self-doubt."
"Hillel said: Do not separate yourself from the community; do not be sure of yourself until the day you die; do not condemn your neighbor until you have stood in his place; do not make a statement which is not readily understood thinking that it will eventually be understood." [Pirke Avot 2:4]
Of course Chabad is about self-improvement and always striving to better oneself. No one is perfect. I know I certainly am not.
I think what the poster meant (correct me if I'm wrong) is that we are more confident in our belief that G-D exists and what our mission is on earth.
You got it. Of course to have no self-doubt whatsoever would be non-Jewish in nature; we must necessarily doubt and ask questions in order to make our faith all the stronger. However, the kind of left-wing self-hating doubt that is all too common, and the doubt that stems from trying to be secular and devout simultaneously, is not present with the Lubavitchers, in my admittedly limited knowledge of the group.
Ok, I'm good with that. In fact, I wish I had something near that level of surety, which is what got me looking at Chabad in the first place.
honestly, i'm pretty much utterly confused about my Judaism right now, so I haven't got any opinions that I'm 100% attached to, except that I have to figure it out before I have kids, or how can I raise them Jewish?
On the other hand, when one is looking so hard for something, how does one distinguish between what is right and what presents itself as right?