Hi Rules that would match an element without any tags are not allowed. It might be possible to allow that, but I think that it would be slow. Most nodes have no tags and are just part of some way, any rule that matches on the absence of a tag would select almost all of the nodes. If anyone wants to experiment then please go ahead, it could be that I am wrong and it can be done reasonably quickly. As things are however, it is intentional that the rules you are trying do not work.
Line: ( highway!=* | oneway!=*) { deletealltags }
This would match a way with no tags, so is not allowed.
Similar error is given when comparing expression with this line: oneway!=* { deletealltags }
This too.
Tt seems != works fine but only if there is an equal comparision first like in this line that gives no error: highway=* & oneway !=* { deletealltags }
Adding the highway=*, means that it could not match a way without tags, and is therefore allowed. Cheers Steve