revision: Weaken language in Contrarian update (#57)

Author: aapoalas

pages/blog/garbage-collection-is-contrarian.md

@@ -471,15 +471,11 @@ contrary!
 
 This post received some excellent feedback / pushback on
 [Lobsters](https://lobste.rs/s/jydyuw/garbage_collected_handles_are_lifetime).
-While I do not agree with what is, perhaps, the thrust of the feedback
-("contravariance has nothing to do with GC or self-reference" or in other words
-that this entire approach is flawed), the following discussion did strongly
-underline a meaningful point: a fully safe representation of unrooted handles is
-possible as shown by [`gc-arena`](https://github.com/kyren/gc-arena) and it
-relies on _invariance_ which can be viewed as a combination of covariance and
-contravariance.
-
-In terms of contravariant references, this is exactly what I get with the
+That discussion brought up a great point that I had overlooked/forgotten: a
+fully safe representation of unrooted handles is possible as shown by
+[`gc-arena`](https://github.com/kyren/gc-arena) and it relies on _invariance_
+which can be viewed as a combination of covariance and contravariance. In terms
+of contravariant references, this is exactly (or close to) what I get with the
 combination of a contravariant reference and a covariant reference of a proof
 value:
 
@@ -493,10 +489,10 @@ The difference between the proven `gc-arena` solution based on invariance and my
 approach based on contravariant references (currently unsound/incomplete,
 requiring runtime checks or new Rust features to make it safe) is, I believe
 (again without proof), that the invariant approach gives the "least upper bound"
-of the solution with a lot of limitations (basically, garbage collection must
-happen outside of the interpreter's Rust call stack thereby forcing a stackless
-interpreter design, and heap data cannot be accessed mutably even in a
-single-threaded system; I recommend reading
+of the solution with strong limitations (garbage collection must happen outside
+of the interpreter's Rust call stack thereby forcing a stackless interpreter
+design, and heap data cannot be accessed mutably even in a single-threaded
+system; I recommend reading
 [this](https://kyju.org/blog/rust-safe-garbage-collection/) blog post and its
 [follow-up](https://kyju.org/blog/piccolo-a-stackless-lua-interpreter/) for more
 details) whereas the contravariant approach seems to give the "greatest lower