Ignore the quoted post. It's bad advice. The same could be said about not getting your instrument rating and stopping at the ppl or not getting your commercial after finishing your instrument. There is always something new to learn but there is also absolutely nothing wrong with stopping at the sport pilot license if you just plan on doing day vfr trips with 2 people or less. When you do get your certificate, both your instructor and DPE have tested you and said you are competent to fly as a sport pilot. As long as the flying you want to do stays within the limits of a SPL there is no reason to spend more time and money on a PPL unless that is what you really want to do. You are just as safe as anyone who finished their PPL, you just have a few more limitations.
The advice to not take anyone else for the first 100 hours is equally as perplexing. You will be the most proficient at basic flying and most risk adverse right after you pass the check ride. Statistics say that you are actually less safe after you get a few hundred hours under your belt because pilots start to relax some of their self imposed limits as they gain hours but not experience. Maybe not everyone here experienced the same thing but when I had 250 hours I thought I really knew how to fly well until I had a few humbling experiences all because I stretched further outside my comfort zone than I should have. I was certainly a safer pilot right after the checkride than I initially was at 250 hours mostly because I was more risk adverse. You will never be more alert, focused, and trying to do everything right than you will be when you take your first passenger up after passing the checkride.
Enjoy the SPL, don't let others tell you that you aren't as good as them because you stopped at the SPL, don't make yourself believe that you are any less safe flying with a SPL than a PPL, and as you build hours always make sure you have an instructor with you if you want to try and expand your comfort zone and always stick to your limits while you continue to learn.