Small comment tweaks

[miekg]

Some post #668 comments nits.

[codecov-io]

Codecov Report

Merging #678 into master will decrease coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #678      +/-   ##
==========================================
- Coverage   58.22%   58.17%   -0.05%     
==========================================
  Files          37       37              
  Lines       10076    10074       -2     
==========================================
- Hits         5867     5861       -6     
- Misses       3162     3165       +3     
- Partials     1047     1048       +1

Impacted Files	Coverage Δ
msg.go	78.71% <100%> (-0.7%)	⬇️

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