can Continental one pass miles be bought from other travelers?

Miles are non-transferable in a sense, but they can be legally given as a gift for a "nominal fee". I just gave my daughter United Miles to keep her account active, and it cost me $99.50 to transfer 2000 miles. The airlines will typically deal in increments of 1000 miles only.

Best to check it with their web site.

Some airlines do allow it, but not all.