OP: I haven't read the thread, and hopefully you got some good replies. But, I want to throw out there:
DS1: Slept well at night from birth - 1-2 wakings for a nurse or diaper change, and back to sleep. He's now 19, and has always slept well.
DD1: Nightmare for about her first year (including crying/screaming jags lasting from 11:00 pm to 3:00 am every single night for about 3-4 months). Waking once or twice a night by a year and a half. Sleeping through the night since about age two. She's almost nine.
DS2: Great sleeper from day one. He slept six hours straight in the hospital the very first night, woke up, had a good nurse, and went back to sleep for another 2-3 hours. He's now 6.5, and we've never had sleep issues with him - not ever.
DD2: Ugh. Ugh. Ugh. She was waking up at least 3-4 times a night at 15 months - maybe more. Sometimes, she'd take a long nap early in the morning, sometimes in the afternoon, sometimes not at all, sometimes a couple of cat naps - no pattern, ever. At about age two, she finally started sleeping through the night most nights, but that means about 8-9 hours. She still (2.5 - she'll be three in June) has no regular pattern of naps - today was about 20 minutes, while latched at the breast, starting at about 4:00. Yesterday was about two hours, starting at 3:00. A couple of days ago, she didn't take a nap at all. One night last week, she passed out at about 6:30, and slept for two full hours, then woke up bright-eyed and bushy-tailed, and didn't go to sleep until after 2:00 am! She has the wonkiest sleep I've ever seen.
They're all different. You're not doing anything wrong. (And, fwiw, after 19+ years at this parenting game, I'm almost willing to bet money that at least some of the moms at the park are full of it.)