Version: unspecified (using KDE 4.5.3) OS: Linux one can start typing the name of a file on the keyboard and the directory focus is moved to the matching files. Very rarely does a file start with a space. Therefore pressing space should scroll down the directory content as it is commonly does in internet browsers. Reproducible: Didn't try
This would be inconsistent with everything. The file dialog idn't a web browser, and the "space to scroll one page down" paradigm is only used for apps that display static paginated or linear content that does not respond to text input. None of that describes the file open/save dialog.