Not possible to compare two re. jpeg artifacts because first was 800 wide and repost is 1024. Larger file will require proportionately more compression to arrive at file size target.

You mention an interesting point Artie, re. the size change after posting. I have noticed this but not to the degree you describe (>50k decrease in size). Typically if I save a jpeg at slightly over 200k it will squeeze under the BPN limit.

Clearly vBulletin seems to be manipulating the image before posting and in recent days it seems to be reducing image size more than normal. This could be related to the problems we have seen at the site over the past few days. Nothing scientific, but I have noticed a lot more images posted lately that are noisy with jpeg artifacts and are a lot smaller than the 200k limit. I think James is working on all this.