alt Hacker NewsCommon or uncommon, its extremely unprofessional. You know when you are dealing with a kid or with professional who actually wants to get hired and has some manners.
Sharing other's company secrets by mistake, using other company's resources in ways that are definitely forbidden - is this a person you really want to hire since they will behave the same in your company? Is this a person you want to give trust with some internals?
In market with 100s or applicants thats enough to disqualify anybody who actually needs an interview or two to get hired.
Maybe this is just an agree to disagree moment, but literally no one I know would consider this unprofessional at all.
I've been in management for the past decade and interviewed a few hundred candidates in that time. Never once did I ask or care who owned the laptop they were using.
And similarly, if someone on my team used their work laptop for an interview, I wouldn't care at all.