Can you give me a little more information on your renaming process? The underline is there to denote an out of scale condition. If you are working in draft and want to change the dimension from a number to a word, select the dimension and when the ribbon bar appears, chose the "modify dimension type" - it's the button a little more than half way across the ribbon and has an "X" in it. Select it and a drop down will appear. At the bottom is the choice for "blank". This will blank out the number. Then select "modify prefix". You can enter prefix, suffic, superfix and subfix information and it will put that in the dimension.
If this is not what you are looking for, let me know, I'm sure we can figure out a solution.
This also assumes you are not changing a dimension on a draft view for a part that is driven by a 3D model. If this is the case, you will need to change the 3D model and the draft view will automatically update to the new dimension.
Right click on the dimension then Properties.
Click the Terminator and Symbol tab
Towards the bottom of the form is Symbol > Not to Scale.
It will be set to Underline.
In the drop-down select None
This will get rid of the underline.
