I like the concept of indicating the difficulty of a puzzle, especially the eraser symbol which was used in the Toketa contest.

Should we implement something similar for the WPC as well ? (It will help people pick and choose puzzle and avoid people whining that a particular puzzle required trial/intuition)

We can, since we have testers who are capable of providing the input. But do we want to risk it in a WPC? Here too, in comments there are few people saying they prefer the ones without the eraser, I don't think it stops the whining entirely if we do this and put in erasers.

People do not prefer puzzles with erasers, but does that mean that we should not have puzzles like Snake, Curve Data, etc?
The basic intention is that we will avoid the eraser symbol in puzzles which do not require tweaking.

Although the puzzles which require tweaking are obvious we can indicate that within those which ones require more tweaking.

Also this is just one possibility there can be other symbols to represent other things, for example a light bulb could indicate that this puzzle requires a bit of out of the box thinking.

I would prefer snakes like the ones on PR, which were logical, but people still preferred to solve with tweaking. However, we can go with, this puzzle is "better solved" by tweaking though there is a logical path in our initial description and then I think it would be fine. Toketa have a few eraser puzzles on volume 3 which I solved logically.