I have separated out the alternate, simple proposal I made in the longer reply earlier in this thread (which also covers some "philosophical" issues) which DOES NOT OBVIATE FUTURE ENHANCEMENTS:

In the Compare/alt-Compare menu (similar canges for alt-F4), change the middle line of the prompt to:

"tag files that aIdentical (Y) Unique (Y) Newer (Y) Older (Y) SameD (Y)"

Where I've put in "SameD" (or maybe "SameDt"?) instead of "Differ" to avoid future confusion -- If anyone has an alternate word to use, PLEASE suggest it... I might like to see Unique and Identical swaped in the line, but that's cosmetic. The word "tag" is not very good either, I would really like to see:

"for files that aUnique (T) Identical (U) Newer (-) Older (T) SameD (-)" OR
"for files that aUnique(Tg) Identical(Un) Newer(--) Older(Tg) SameD(--)"

With T/U/- (or clearer Tg/Un/--) a three way choice for each one -- the highlighted letter toggles between "Tg" and "--" while (say) shift-letter toggles to "Un" and back to "--" (keeping the current keystrokes as is...). Note: for "SameD" only the S is highlighted -- the D is uppercase but not a highlight...

---

The bottom line changes to one of (K toggles the form):

"ignore Case(N) and sFn(Y), checK(Bin.) and (Ver.) <-+ok ..." OR
"ignore Case(N) and sFn(Y), checK(Bin.), use(Ver.) <-+ok ..."

A "K" toggles between the "and" and "use" formats which differ as to whether the date/time/version is used as part of the "identical" decision/checks or merely to determine how to select Newer/Older/SameD for files that are not Unique or Identical.

The choices for "use"/"and" are Ver./Date/Time/none -- D toggles Date/none, V toggles Ver./none, T cycles Time/Date/none -- Maybe "e" [highlight in each of Ver/Date/Time/none] could cycle through all 4 choices... -- Time covers the whole timestamp while Date means that only the date is used...

For "checK" the choices [maybe "Body" is better than "Bin."] are Bin./siZe/name (B toggles Bin./name, Z toggles siZe/name). Maybe "h" could cycle through all three...

C and F toggle their Y/N settings.

I like this form of the line since it reflects the algorithm used...:

First, match up files, possibly ignoring case/sfn -- if no match, go to Unique,

Second, check whether the matched files agree in size or body/binary or just name (that's "none"), and, if the K toggle is on "and", the selected one of ver./date/time/none. -- If they check out, go to Identical...

Third, "use" the date/ver/time choice to classify file (pairs) that are not unique/identical into one of Newer/Older/SameD.

Eventually, I hope that we can extend the Tg/Un/-- choice for each one of the categories into a fuller set of marking operations (tags and attributes...).

I think the meaning of all of the above is fairly obvious and intuitive. Note that I have been careful to retain the meaning of ALL of the current keystrokes -- they have exactly the same effect as they do in the current Compare/alt-Compare menu/prompt...