Both tags now have questions with +5 votes. What am I missing?
Users with more than 2500 reputation (1250 on beta sites) and a total answer score of 5 or more on a given tag may suggest synonyms for that tag.
So you as a user would need to have an answer score (total upvotes minus downvotes) of 5 or more on md-80 to suggest a synonym for it. It still needs 4 others that also have a score of 5 or more to vote to be approved.
If you don't meet that requirement (or even if you do), you can post a question here on meta. If a mod agrees with your suggestion they can make the change. It also allows discussion, as some synonyms are not as straightforward as they seem at first glance.