Signs holding player data breaks certain commands.

Signs remember which player last edited them, and certain commands such as testforblocks or execute commands (if blocks condition) read this data and throw unintuitive negatives. Two signs can be the same, but be considered different because different players (or no player) edited them last.

Place two identical blank signs with the same orientation etc. Test the blocks with the testforblocks command i.e. “/testforblocks [sign 1 coordinates] [sign 1 coordinates] [sign 2 coordinates]“ this provides a positive result “1 blocks compared“. Now right click sign 1 to edit it and add text to the sign. Run the command again, and you get a negative result, as expected. Edit sign 1 to delete its text and make it blank again, run the command again and it throws an unexpected negative result - even though the signs are now identical again.

Expected result: The command should yield a positive result as the two signs are identical.

Actual result: The command throws a negative result. “Source and destination are not identical“.