I always like to see articles promoting web accessibility - so thanks for writing this :)
A couple of minor comments:
just as alt text should be meaningful (or empty for decorative images) link text also needs to give a clear indication of the link target. As such I would replace "site" with something more descriptive like "alt text recommendations".
achieving good colour contrast is not just a matter of picking colours opposite each other on the colour wheel. For example your chosen example of red/green is a combination associated with one of the most common forms of colour-blindness: for some it would render content illegible. I wouldn't necessarily remove the example; but I would add a comment warning that this should also be considered ;)
For further actions, you may consider blocking this person and/or reporting abuse
We're a place where coders share, stay up-to-date and grow their careers.
I always like to see articles promoting web accessibility - so thanks for writing this :)
A couple of minor comments: