Well, it's up to you if you want horribly mangled text rendering ;-) I won't make a judgement call one way or another on the font weight on the site. I'm just telling you that your font rendering is misconfigured. This is why you can't read that text.
Even for higher font weights, the rendering in your example is atrocious. Compare the sibling post's thicker fonts to yours. Notice how yours are fuzzy on the outside? His are crisp. Now, pick a website with a font you like. Shrink the page down so the characters are really small. Look at the characters closely. Do you see how it looks smeared and how there are pixels of different colours (not just black and gray)? This is the result of the misconfiguration. Good hinting will allow you to shrink the font to a very small size and still have good anti-aliasing. Without playing with it, I don't know if it's just that you have the DPI set wrong, or if you have auto-hinting turned on (which you should never do now that the hinting algorithms are no longer patented), or possibly something else.
If you ever decide to look into it, probably the best keywords to search for is "anti-alias" and "hinting". It seems silly to me to put up with such awful rendering just because you are too stubborn to consider the possibility that you are wrong.
