I've read twice somewhere a year ago that it could get you banned more than anything.
All information that you find on youtube & forums is pure speculation. Only Sony knows when & why to ban an account or console.
The common sense says that if Sony has the requisite of be on the latest firmware version to access PSN, and you are accessing it from a lower version, it could be a reason to be banned. But that's not confirmed.
Some facts are:
- It is possible to access PSN using the proxy method. But it 100% detectable. It doesn't spoof the FW version.
- If you login using the proxy method, it is uncertain if you're flagged or not, since the bans normally occurs days or weeks later.
- If you cheat online, use mods/menus, harass other players or play games like CoD, GTAV, Destiny and other games with CFW syscalls enabled, it's almost 100% sure that you'll be banned.
Some recommendations are:
1- Spoof your real IDPS/PSID with spare ones whenever it is possible.
2- Use a secondary PSN account to go online. If the account is banned, your purchased content will not be affected.
3- Disable automatic login to PSN and disable CFW syscalls before go online.
4- Don't use cheats or mods/menus and never run homebrews while you're online.
5- Keep a low profile.