Comment multi-mappings not created in the diff

[tsantalis]

JabRef/jabref-koppor#716
jabgui/src/test/java/org/jabref/gui/edit/ReplaceStringViewModelTest.java

// replace "Informatics" in the JOURNALTITLE field to "replaceText" in the BibEntry
exists 4 times on the left, and it is broken down to 4 x 6 = 24

UMLCommentListDiff makes 4 x 24 = 96 mappings for these comments, which are not displayed in the diff.

[pouryafard75]

Replicated here

[pouryafard75]

@tsantalis There are no matched comments on the right-hand side for lines 66-91

[pouryafard75]

@tsantalis They are actually reported in the added comments

[pouryafard75]

Break on line 29 and inspect comment diff list