Does anyone know what this redish/purplish vertical line is?

[Fateepee]

When I hover over it, I get my name popping up but I have no clue what it is. I tried to turn off review tracking and commenting all to no avail.
Thoughts?

[#2]

Can you upload a copy of the document so that we can investigate.

[#3]

@Doug_Robbins_Word_MVP 

Hi Doug,

The problem is now gone. I don't know exactly why. I think it might have to do with the fact that I had one instance of word with the document open running on my main pc, and I was editing the document on my laptop, which was stored on my OneDrive.

No further investigation needed.

Thanks for helping out.

[#4]

@Fateepee 

My guess is that you were seeing the "flags" that represent different users in a co-authoring environment. Since the document was open on both your PC and your laptop, Word/OneDrive identified this as two different users. 

[#5]

Thanks.
That makes total sense.