The flawed human brain and its ability to remember is merely evidence of a flawed observer, and not evidence of a flawed reality.
The processing your brain does to fill in details is irrelevant when there are multiple methods of observation and multiple observers, and all agree with reasonable precision. When multiple observers can measure an object and find that it has volume and mass, we can all agree that the thing exists. We might disagree on what to name it, or what it "means", but it'd be pointless to argue that it might really not be there.
While one could argue that everything, including all the other observers, are a product of my imagination, it isn't productive to do so. Whether it is all in my head (or in a supercomputer and I'm really just a simulation) isn't a useful theory. I can't do anything with that theory. It is untestable, and thus is mere superstition.
In short, objective reality is a good model for...reality. And, so, it makes sense to behave as though jumping off of a cliff will probably end ones existence.
I believe the notion that someone on HN would be "pro objective reality" (whatever that means...I'm not sure there is any way to win against what is, so why fight against it?) comes from the fact that we are all mostly nerdy, science-oriented, and we tend to be more likely to know how things (where "things" can be mechanical, biological, electrical, etc.) work. We know that when you feed voltage into a particular semi-conductor, the same thing happens every time...so, we tend to be less likely to fall into the trap of thinking things happen because of magic or because we imagined they happened or whatever.
In short, I reckon accepting objective reality has a net positive value in my life. I'm not sure how denying reality would do me any good. I'm pretty pragmatic, and I like having some level of control over stuff in my life, so I reckon I'm a believer.