Are we allowed to buy and sell players on the transfer market for profit?

I follow the forum and read people all the time saying they get transfer banned, or worse losing their EA account.

I've never been banned for over a decade playing EA Games. But I have seen warning screens for simply just buying and selling players on the market.

Can we get a definitive answer for this? Are people getting banned due to other complications or other stuff they are doing?

For example, this weekend I purchased many Malen Pro Live cards from the market for ~14K. I am hoping they go up in the future to a point where I can make decent profit on them, so I can afford better players for my team.

Is this allowed? Or should I just quick sell all of them and save myself the headache? I am so confused as to why people are getting transfer bans, as I keep reading here and on Reddit.