@azaroth is right.

Aside from doctoring evidence, there is a way to appear as another person in global. So, if this person wanted to get your friend suspended with screenshot evidence from global chat, perhaps.

However, I don’t understand how spamming chat could possibly be a reason to suspend*. Considering you can mute anyone in the player list easily. Are you absolutely sure this was the reason? Ask them to share the suspension reason via a screenshot.

Additionally, in the past it has been suggested that Funcom would view the chat logs of the server regarding chat related reports. So, if we’re to believe they’re that thorough, then it would stand to reason they’d have viewed that evidence, right?

*A suspension is temporary. A ban is permanent.