i have been going throughout this issue on a Telecommunication project.
However the persona and the usage are different, the old journeys have been translated from accordion off the wizard journey ( for application reason ).
Its mobile reference contains same ideology; also the modus behind the journey is a shortened wizard.
The validations are made on a tooltip which is pointing down the form in order to do not expand/contract the interface.
However an accordion has a vertical progression and analyzation ( in which the progression of the journey mental model would be vertical as well).
User can - if needed - to get back in order to review/change his/her credentials.
Running heuristic evaluation of the user focused with the project in this case, can eventually help the interface to provide a wider chance to enter the tunnel of registration.
Sometimes it could be harsh for the user going through it since it depends on the
information he/she is providing.
Accordion are fine, also giving the user the chance to review all his step once he compiled correctly the needed one.
However having a 'summary page' and giving the chance to the user to review the registration process in divided 'steps' could lead to a 50-50 register success, gave by the
clearance of its process.
Consider having also - in order to have a proactive registering process - to 'divide' as less as you can the steps which are in between the point (A)Register needed to (B)Be successful on the task you were doing before registering - or just simply continue what you were doing before -.
Having a simpler registration form - asking Mandatory information in which are needed to create the persona ID within your system - you can let the user modify his/her credentials once is in-to the system.
Would like to void in this case to let the user think too much to register or not:
The user is getting registered right now. How can i add value?
"We need your information, but the user need to do quickly as possible. Also be able to continue what he/she was doing before registering.
Do not cut the user's attention with the registration form too much."
| Doesn't matter what you are using, but How you are using it and who is telling the
information ( with A Tone of Voice ). Lead the user by asking exactly ( without assuming
too many steps if not needed ) the action he/she Must do in order to accomplish his
success; and your success.