While Gruber is often labeled writer, many forget that he also was a (web) designer. As such it is very regrettable that he never included floats or center options.

Especially considering that the whole reason why he created Markdown was to make it easrier for authors (writers) to include basic HTML. WIthout needing to type out all those < & > and other attributes.

Semantically pull is most often used for pull-quotes, thus something which serves to highlight. Left or right-aligning an image actually gives it less focus.