[DevExpress Support Team: CLONED FROM T676140: Rich Comments: disable for certain file types]
Clicking into the line did not revert the rich formatting. Even after editing the line, the underlining persisted and moved the caret off-by-one due to the hidden underscore.
But this should probably in a ticket of its own.
Try the following steps:1. Copy one of those connection strings (which are NOT commented out) a couple of times so you have at least 3 lines.
2. Comment out the 2nd one by moving the cursor into the line and invoking the Visual Studio command "Comment Selection" (Ctrl+E, C or similar, depending on key bindings). Do NOT explicitly select the element, Visual Studio will take care of that.
3. Verify that this now commented out 2nd line behaves correctly.
4. Comment out the 3rd line by doing the same as in step 2.
5. Verify that the 3rd line behaves correctly, but the 2nd line is now broken.
That reproduces nicely for me, every time.