Here is an image taken with an iPhone 6 and uploaded as-is:
Here is that same image when shrunk down in MS Paint and then uploaded to the gallery:
If you zoom in in the gallery on the first image, with the very first click, it becomes sharp and clear. I'm not sure why the image shows up blurry in it's natural form, though, and it means that the image has to be altered on a
PC before being uploaded if it is to show up clear when posting it to the forum. Is it the size of the image? I tried this with many, and they all are 3264x2448, and all show up blurry in the gallery, which is a bit maddening

(I went and manually re-sized the ones I wanted to post in the forum, and deleted the others except this example to demonstrate the issue with).