Here's an example of scale differences I've noticed. The figure on the left is Emhar's WWI British infantry and the one on the right is an old Academy tank commander, but both are said to be 1:35. Neither of them are suitable for the tank. Comments anyone?

The ruler is your friend. In 1:35th scale, a 5'10" man is exactly two inches tall. Many Asian manufacturers issue figures designed to typical East Asian stature (and sometimes short even for them). Tamiya figures typically stand about 5'5" in scale, and their earliest figures from 1970 were even shorter.
The World War Two generation was generally shorter than their children and grandchildren are (no vitamin fortified everything during the Great Depression), and a six foot man would have been nicknamed "Stretch" in the US Army. However, even for the 1940's, the Tamiya and Academy figures are still very short guys if they are intended to depict Americans or Europeans.

This is an ongoing debate. There are differences in all people so some variations are good. There are also some well known differences between manufactures - Verlinden is typically bigger than Warrior - not as big as the one you showed.
There are also well known differences between figure material, injected plastic is usually smaller compared to resin. And you nailed the 'soft plastic' material figures are usually closer to 1/32 vs. 1/35.
This is why there is a ton of figure mixing in dioramas.

Yup I agree with Scott. It's more realistic to have soldiers of varying height. However, if the weapons and kit are different in scale too, it will be a prob. In the pic below, the fig on the far left is Verlinden, and much taller than the pointing DML fig, but the weapons are the same size, so it looked OK.

Further, the figure on the left appears to be a "toy soldier" which is typically scaled at 1/32 (54mm). That becomes even more muddied because some sculptors use the eyes as the measuring point for 54mm while others use the top of the head.

David has a point about people being different sizes, however 1/32 (54mm) & 1/35 are too far apart to combine convincingly. In addition I suspect that some less than scrupulous manufacturers have old 1/32 dies that they are now selling the products of as the more fashionable 1/35. I bought a set of Academy German Tank Crew who, I suspect belong in this category, as they are giants compared with either DML or Tamiya figures. The old Airfix poly figures & Multipose are definitely 54mm/1/32, & were sold as such. Unless they are under scale you can't use them for 1/35th. That Emhar infantryman looks like a 1/32 figure to me. The older Eastern figures from Tamiya etc are real dwarfs, & they are out of proportion too, because a short man will tend to look more "stocky" compared to his average taller colleague. However, note in WW1, the British "Pals" battalions included a "Bantam" battalion, in which all the men were under 5' in height. Conversely in WW2, German conscripts could be as young as 16, so would look smaller & slimmer than a full grown bloke (e.g.HJ). Another thing that isn't widely realised is that WW2 British paras tended to be small wiry blokes, due to the primitive parachute technology available; General Urquartwho commanded 1st Airborne @ Arnhem was told he was too big to jump, so travelled in a glider!

Hi All,
Thinking about the stature of soldiers, it would seem obvious that HJ, being young men - even boys would be smaller that fully grown adults.
But would their uniforms have been as 'too scale' and as well fitting?
If you were to imagine that the two figures in Bruce's original post were HJ from (say)1944,
would the smaller figure have the same well fitting uniform. Irealize that there were different sized uniforms produced but wouldn't there have been a 'sorry Hans that's the smallest tunic we do' element coming into play.
Tom