I really like to start writing some class and method comments to make Pharo image more beginner friendly.

This would be realllllllllly coool.
Did you check the class comment template because I wrote it thinking about this.

What I think would be great is to have great comments for the basic classes. Because as a newby such classes are really important.

For example I would like to enhance the symbol class comment to include the snippet sent by henrik

| s1 s2 |
s1 := 1234 asString. s2 := 1234 asString.
s1 = s2. "true" s1 == s2. "false"
s1 asSymbol = s2 asSymbol. "true" s1 asSymbol == s2 asSymbol. "true"
(s1 class allInstances select: [:s | s = s1 ]) size. "2" (s1 asSymbol class allInstances select: [:s | s = s1 asSymbol ]) size. "1"
[ #stringA = #stringB ] bench. "26,812,864 per second" [ 'StringA' = 'StringB' ] bench. "3,492,987 per second"

Are there any guidelines when and how to comment classes and methods ? What about inline comments ?