Holy guacamole! You are uploading HUGE images.
Just to clarify the image sizing/color/quality issue… timethief, did you know that WordPress.com has a built in feature to resize and compress images for you so you don't have to do it on your computer before you upload?
For example, check out this version of the image you linked earlier: http://chilecopadevino.files.wordpress.com/2013/09/img_0812.jpg?w=150
Resizing before uploading isn't required like it used to be.
In the past, you had to resize before uploading but you don't have to any more because WordPress.com does it automatically for you! Regarding color and sharpness, if you are a photographer (probably most people aren't) or a graphics professional, you might want to resize images on your own, maybe—but if you did resize manually, then you would want to resize them to double the image display size so they will work properly on retina displays (something new to consider). Also, note that resizing images with a graphics program manually will of course also result in loss of color and quality (that's inevitable when compression is used), the only difference is that if you did it manually you'd have a little bit more control. I know you've helped troubleshoot image issues in the past and probably have seen some problems and that's why you posted what you did. However, also keep in mind that WordPress.com is always making good changes behind the scenes too, and things like image compression, quality, and color have likely been improved compared to when you've seen people have problems with those things in the past—and probably based on some of those past issues you remember. Also, I recall that in many cases in the past, the problems happened when an non-standard color profile was used when it shouldn't be (i.e. saving with a print color profile like Adobe RGB compared to a screen color profile like sRBG which is designed for monitors and works best on the web).
@chilecopadevino, thanks for replying on the other thread. I'd like to look into the thumbnail resizing in more detail, and I've posted more info. for you on the other thread.