I don't have any sorting rules for any of my playlists, and they all sort by "seq"
It makes a difference depending upon how you begin playback of the playlist.
if you apply sorting rules via "customise current view", then, regardless of sequence order, if you use the "play" button in the playlist header, MC sends the tracks to playing now as per the defined sorting rules.
I consider this a bug. Regardless of how a playlist is presented, it should always play back in sequence order.If you either double click, or right click > play, on a playlist in the tree, the tracks are played back in sequence order, regardless of the current sorting of the list, be it by column header clicks or sorting rules.
If you remove any sorting rules as described by bennyd above, the play button in the playlist header works as expected.
For the record, I just added a new playlist (F8) and it defaulted to no sorting rules in the "customise current view" dialogue, sorting by sequence as expected.
Tools->Options->Tree & View->Sorting->Save changes on list header clicks
This will remember your way of sorting. You define sorting simply by clicking the header of the desired column. That's how it suppose to work, anyway.
This option is OK if you're just starting out with your views and have still to finalise how you want them to default, once you've done that however, I'd recommend turning it off. That way, if you fancy seeing your list sorted another way temporarily, say by name for example, you can click on the name header. this is not saved, so the next time you load that view, or hit refresh, everything will be restored to your default sorting rules as laid out in the "customise current view" dialogue.
One thing I noticed is that after making a playlist and then including into a smarlist with no sort rules, the playlist order is not honored and Im not even sure what the actual sort order is.
I'm 99% certain that viewschemes with no sorting rules default to the "media type / artist / album" preset rule. adding these columns to a test list appears to bear that out: