Like I said in my first post; there's technically a method to the madness, but it's so complex and obtuse that it might as well be random. You can do some things that can affect your odds, but a lot of it is still left up to right-place-right-time. There's a balance to strike between having something accessible with a broad appeal that lots of people are going to like, and something niche and unique that doesn't look like everything else out there.
For example: 'promote your stuff here' is no different from any other promo post on this forum, so why would anyone click on it instead of any of the others? On the other hand something like 'Tokusatsu (small niche genre of Japanese television. Think Power Rangers or Ultraman) creators share your comic here!' is so small and niche that basically nobody is going to fit the bill and want to engage with that post.
So something in the middle; the 'post your latest page' thread is a great example of this. It's something that everyone can do, no matter what type of comic they're making or what sort of skill level they have, but it lets each person post something unique. People are going to want to click on it to see what everyone's most recent art looks like, and they're more likely to want to engage with it.
Even then, there's an element of randomness; if you post it at the wrong time of day when not many people are on, then it's off the front page before people who would have engaged with your post are looking, and they usually don't go digging through stuff that's too far off the front page. If you don't happen to get any good artists sharing their stuff then it'll look like amateur hour and nobody really cares. Alternatively, if you ONLY get really skilled artists posting, then less-experienced creators might get intimidated and not feel comfortable sharing their stuff.
All of those things are, to some degree or another, entirely out of your control. Sometimes it works, sometimes it doesn't, which is why I said you just have to keep placing your bet until it pays off.