Fix issues brought up in melpa pull request

~~Especially at https://github.com/melpa/melpa/pull/6352#issuecomment-520111304.~~ (EDIT: Issues at that particular comment are all addressed except for that regarding special-mode, which is opened as new issue at https://github.com/bradyt/dart-server/issues/8.)

This is a note to either fix these issues, or file each unresolved issue to the issue tracker here, or even add as failing tests in the testing framework.

Review the issues raised in melpa/melpa pull request #6352, especially the referenced issue comment, and check the related special-mode issue at dart-server#8. Use the project's testing framework to determine which concerns remain unresolved. Done means fixing each remaining issue, filing it in this tracker, or adding it as a failing test.

Written by the indexing model from the issue text.