EDIT: Answers have pointed out my information is outdated. Please read the answers before concluding anything from my question!
Question before editing:
DB famously accept only payment cards, not passports or national ID cards, as identification on the train. Such identification is a requirement for online tickets. Do I need such identification for paper tickets?
According to Mark Smith https://www.seat61.com/Germany-trains.htm what you state used to be true but no longer is:
If you wanted to use a German Railways print-at-home ticket (shown as online ticket on bahn.de) you used to have to show your credit or debit card as I.D. on board the train. I'm glad to say that this changed in October 2016, all you now need is a passport or other recognised ID to prove your name to support a print-at-home online ticket. You may or may not be asked for it by the conductor.
Only one name is necessary to support a print-at-home ticket, even if the ticket covers more than one passenger.
No ID is necessary if you select tickets by mail, as conventional train tickets have no names on them and need no ID.
Your information appears to be outdated:
The following means of identification are accepted during ticket inspection:
German ID card
German passport
Children's passport
Electronic residence permit
Asylum registration confirmation (BüMA),
European ID card
International passport
BahnCard (in accordance with the Conditions of Carriage, valid only in conjunction with a photo ID, which may have to be presented on occasion).
The question you are linking to is outdated. Since October 1st 2016, you can use any passport or a national id card from an EEA country as identification when travelling with an online ticket.
For paper tickets bought from a ticket counter or a ticket machine, it depends on the type of ticket. Most tickets are not bound to a specific person, and for these you do not need any id at all. There are however several kinds of daily passes, like e.g. the Schönes-Wochenende-Ticket, which are bound to a specific person or persons. With these tickets, you usually have to write the name of the passengers on the paper ticket, and the passengers must be able to present a valid id to the ticket inspector.
