Carbon steerer tube scratch (inside the tube) - how bad is it? Today I looked into my steerer tube and saw this:

Since Im new to carbon frame, I cannot decide if this is a serious problem which has to be fixed asap, or just a minor scratch on the surface. It dosent look cracked, not deep, probably caused by my expander plug...
Thanks for your toughts, maybe some of you had the same issue
Best
Old question.  Not sure if anyone is interested, but here is a shot.
Qualifiyer: I am not a bicycle frame Designer or bike repair person; however I have spent 30 years in the aircraft industry telling people how to repair composites.
That picture is a bit misleading, looks like a flash blew out some color &amp; detail.
The tear line &amp; location makes me think this is a fiberglass isolation ply.  If it is, the floppy piece would be white.  Delaminated fiberglass is normally white, bonded is nearly translucent.  The main use for a thin fiberglass isolation ply would be to prevent galvanic corrosion between the carbon &amp; aluminum.  The aluminum will eventually go away via corrosion, again white.  I am assuming the head stem is aluminum.
Also, fiberglass has a 3X modulus of elasticity over carbon.  It's more stretchy.  Probably making it more resistant to the abuse from your expander plug &amp; putting that extra layer between the plug &amp; carbon.
I see no Structural issue here.  a thin coat of room temperature curing resin, paint or even fingernail polish just over the missing fiberglass with a very slight overlap will take care of any potential galvanic corrosion issues.  If not, it will take a long time for the corrosion to do much damage.