Related (the same bug has existed for a long time on Unix-like platforms, where tilde expansion is a stable feature):

• Unix: Emulation of ~ (tilde) expansion for native utilities is syntactically incomplete #20754

• @SteveL-MSFT, note that in addition to the case mentioned in this issue, the following cases are broken too, just as they are (analogously) on Unix-like platforms:

cmd /c echo ~\'foo bar'  # should expand, doesn't
cmd /c echo `~         # shouldn't expand, does
cmd /c echo ~'\'  # shouldn't expand, does

And, with respect to tab-completion:

• Broken tab-completion with file or directory names with spaces in the context of tilde-prefixed paths (~) #20851

@mklement0 I checked my PR branch and your first case works as you expect. For the second case, I don't know if you should expect it not to expand. Even thought you are escaping it, I don't recall another case where it would be treated as a literal. You'd have to enclose it with single-quotes to indicate it's literal. The 3rd case I also don't see any inconsistency in expanding as it resolves to ~\ as the single quotes are not around the tilde.

I checked my PR branch and your first case works as you expect.

Glad to hear it (in my initial response I missed that you were referring to your PR).

For the second case, I don't know if you should expect it not to expand.

By way of analogy: both cmd /c echo `@ and cmd /c echo '@' work to to ensure literal treatment of metacharacter @, so the same should apply here.

The 3rd case I also don't see any inconsistency in expanding as it resolves to ~\ as the single quotes are not around the tilde.

The very purpose of this feature - at least originally - was emulation of the behavior of POSIX-like shells.
You'll find that executing the following from a POSIX-like shell does not result in expansion, and I see no reason to treat the Windows case differently:

# From a POSIX-compatible shell; contrast with: echo ~/ or echo ~/'foo'
# -> '~/'
echo ~'/'

@SteveL-MSFT, speaking of the analogous case; please see:

• Unix-like platforms: native globbing and tilde expansion cannot be prevented with backtick-escaping #21304

• also: Native globbing: Automatic globbing for native commands doesn't work with backtick-escaped spaces #10683

I haven't looked into any technical challenges that may prevent interpreting ` as suggested (you'll need to know early in the parameter-binding process whether a given char. was `-prefixed), but it certainly makes sense to exhibit the suggested behaviors from a user's perspective.