Using WinMerge 126.96.36.199 (Unicode)
In the attached set of three text files (all UTF-8 encoded), there are at most three lines different between any two of them. However, comparing file C-UTF8WithFirstUCAfter4096.txt to either A-UTF8WithFirstUCBefore4096.txt or B-UTF8WithFirstUCBefore4096.txt shows several spurious differences. This happens because WinMerge incorrectly classifies the file as using CP1252 encoding vs. UTF-8. This in turn is apparently due to the first unicode character appearing after byte 4096 in the file.