There are a couple of ways to look at this, and it always about the nuances of degrees. One may argue physicality isn’t in the picture hence it’s not unfaithfulness in the strictest sense of the word. Another may counter that infidelity of the mind/heart is as hurtful as any other form of adultery.

Yet a third may challenge that premise by asking just how much of a person’s thoughts should a partner control, or should it be restricted at all in the first place?

If there were easy answers to matters pertaining to the heart, then relationships wouldn’t be as complex as they are in reality.

I can only say this as it pertains to myself, my values and my character - no, I wouldn’t do that (texting) with a person of a different gender because I know how much that would hurt my wife. After all, I wouldn’t like it if she did it behind my back and one of the bedrocks of a long lasting relationship is to always have each other’s backs.