Don't know if it's a bug or not but, i've got a problem when i use image.
Example :
post 1 (without image)
post 2 (with image) is not marged
post 3 (without image) is not marged to the post 1 and 2
post 4 (without image) is marged to the post 3
Tested with vB 4.0.1 PL2
[EDIT] see your post where you say it's for desing, is it possible to have an option to disable not merging with image ? (next version

)
Thank you !