Basically, if a line begins with double backslash (as is the case with Windows paths on a shared drive), it gets split awkwardly.
Try adding this text to a confluence page
\\Drive\Folder\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\Path\
Notice that confluence inserts a new line in between the first two backslashes, causing the first line to have only one character
When forward slashes are used instead of backslashes, the formatting is correct - i.e. there is no weird split
//Drive/Folder/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/Path/
The formatting using double backslashes should match the formatting with forward slashes