I want to add that this is the case when using the thumbnail content in de detail post page. In that scenario the detail page generates blank image alt information for that thumb. When emebedding the same thumb as an image in the detail page the alt information is there.
Also, in the default blog page (here: http://sodafish.com/blog/) all image tags are blank in the code, while there is tag information entered. But it is not generated.
I want to add this is the same for the portfolio thumbs. Self entered Image alt information is ignored. It’s not blank there though, it seems to take the page title information as image alt information. This is fine, but when entering specific alt information for media files it would be nice to see this generated in the code.