Clarify significance of order of items

[maksverver]

(Not sure if this repo is still active but I'll file the issue just-in-case.)

The current spec does not make it clear what order, if any, entries should be listed in. There is a point to be made that order is entirely immaterial and can vary between different requests. On the other hand, it seems reasonable that the items are ordered in some sensible way, either by publication date or modification date, ascending or descending.

My preference would be: publishers SHOULD (not MUST) order entries by how recently they are modified. That way, consumers can fetch the main feed to get all recent updates, and not follow next_url links unless the last item was an update.

In any case, it would be useful to provide some guidance on how to order items in a feed, to prevent publishers all doing something different for no good reason.

[manton]

I’m not sure if this needs to be spelled out in the spec, but in practice almost all feeds are reverse by date, like blogs.