Your example isn't idiomatic. You would not write begin/end for single-line cases.
Instead it would be:
if ((input = 'y') or (input = 'Y')) then
writeln ('blah blah')
else if ((input = 'n') or (input = 'N')) then
writeln ('blah')
else
writeln ('Input invalid!');
OR even better
case uppercase(input) of
'Y': writeln('blah blah');
'N': writeln('blah');
else
writeln('Input invalid!');
Well if we're doing that, then you wouldn't use the curly brackets in the C style syntax example either. If you just make one ideomatic without making the other ideomatic, the comparison ceases to be fair. Anyway, doing that to both of them would make the comparison pointless, because the point wasn't to compare ideomatic code examples, but to compare the syntax in a general case, so writing them slightly unideomatically to show off the general-case syntax is fine, as long as both are written the same way to control for unrelated variables (like special-case syntactic sugar), which is precisely what the original comparison did: write both code samples in the most general way, and crucially in the same way, so we could directly compare the scanability of syntax. And imo C won by a mile.
TBH? I see them basically the same. My brain probably scans equally faster "b...n" and "e..d" then the direction of the curly brace. And I haven't read or written Pascal since early high-school, ~30 years ago.
Great example. Your C-Code translated to Pascal would be
if (input = 'y') or (input = 'Y') then
begin
writeln ('blah blah');
end
else if (input = 'n') or (input = 'N') then
begin
writeln ('blah');
end
else
begin
writeln ('Input invalid!');
end;
Now this does not look any different then your code.
Except your code does compile but has several errors.
And why should be the double pipe be any better to read than
an "or" statement?
Btw: as you won't need the begin and ends it would look like
if (input = 'y') or (input = 'Y') then
writeln ('blah blah')
else
if (input = 'n') or (input = 'N') then
writeln ('blah')
else
writeln ('Input invalid!');