A redirect import, a disavow file or a bulk edit that contains blank rows behaves unpredictably. Some systems skip them, some error, and some create empty records.
The worst outcome
A blank line in a redirect file that gets interpreted as a rule with an empty source or destination. Depending on the platform, that can produce a redirect affecting far more than intended, and it is not obvious in a list of hundreds of rules.
Clean before every upload
Trim, remove blanks, then check the count matches what you expect. Three seconds against the possibility of a malformed rule going live.
Verify after upload too
Compare the number of rows the system reports having accepted against the number you submitted. A mismatch means something was skipped or merged, and finding that immediately is far cheaper than discovering it from a traffic report weeks later.
Try it: Remove Blank Lines on SeoWolf's Notepad.