DjVu is actually an image format; it would take quite some creativity to come up with a reflow option for that. Internally,
some DjVu files may be structured in rows of symbols, and they may even have an invisible text layer (used for search and copy), but it's even worse when it comes to reformatting than PDF. For instance, even if they do use the row-like encodings, there's nothing calling for them to go in meaningful directions. In other words, there's no concept of a font, margin and so on in the format.
All that said, however, the 90[23] certainly can display DjVu files nicely. Except for reflow, the zoom options appear the same as in pdfviewer, including multipage and column display. Unfortunately that includes the lack of vertical fine-tuning, so it's not ideal for trimming margins.
There's also no provision for page layouts different from the screen, as I found up when opening a file with comic scripts (
Sabrina Online, as it happens). It grew particularly ridiculous when I tried the option to show two pages in landscape mode; despite the menu showing this as one over the other, they were squished in horribly deformed side by side. Normal zoom settings at least aren't deformed.