Known Work Item History Limitations for Links & Attachments
They are two major problems when looking into the history with regard to links.
1. No clue what has changed:
If you remove an attachment and add a completely different one the history will indicate that there was a change (revision gets in incremented by 1), but it won't tell you what has changed since TFS only tracks the numbers (e.g. number of external links).
2. Work Item links are only reflected in history on one side:
You have two work items: item 52 and item 53.
You decide to link item 53 with item 52.
Both items show the work item link under their "Links" tab.
Item 53 shows the new link in the history:
But the history of Item 52 shows no changes at all: