What your masters level business communication course has taught you is one thing. What you are missing that communication in the business world isn't just what you write but the message it sends to others, and email is a very precarious and underestimated form of communication by most people.
I'm in business courses now, and they teach about how critical it is to understand how others take in communication. And all the problems about loosely written emails.
The IT person was clearly bothered by the wink and the nudge and contacted your boss. It seems like a pretty small thing for your boss and the IT person to get upset about, but it does appear it was more than one person.
Are you sure it was just the "wink, wink" alone and not the overall tenor of the communication?
You clearly didn't mean offense, but it is a weird situation all the way around.
If you wanted to work in the different dept, it would have probably worked out better to go through the right channels instead of through winking and nudging. You were also supposed to be completing a task for your boss, and you didn't ask them if it was ok to use that time to try to make connections for different work. It probably made your boss look bad.
If I had an entry level employee who was winking and nudging employees in other depts to work in a dept I didn't manage while completing tasks for the role they are employed for under me...
I mean as an online peer, I get the meaning of your communication. But as your boss, I might feel quite insecure about it, like perhaps you meant things you didn't say or implied you didn't like working for me and didn't take it to me, but to others.
In the end there is one lesson no one teaches in school but too many people learn the hard way: keep emails simple and minimal.
I have seen even the most well written emails destroy careers. Email is good for very logical logistical communications. That's it. Not emotional topics, not heavy discussions, and not for joking around. Not for anything where context and tone matters. Context and tone get lost via the written word and emails can be passed on so easily to unintended audiences and cause extended drama for all. The higher up people go in most professions, the less they tend to email because of all these tricky elements to it.
Keep business emails practical and overly professional.
If you want to joke around, do it face to face. Joking around can be a team builder when done well and in person - because you can see audience and see how they take it and make sure they are in on it. The audience can also get that it's a joke a lot easier. Most of communication is non-verbal, and this is easily forgotten in the business world until people learn it the hard way.
You didn't do anything massively wrong. Take this as a lesson learned about the dangers of misunderstood emails in the workplace and keep doing your job well and find a culture that fits you the best. :)
