Requested feature overview description.
Very often certain tags will be used together with other tags, but should not be implicated to each other. It's also quite easy for users to completely forget about adding applicable tags. Therefore I propose a system to recommend/suggest tags based on already entered tags.
For example, avali should not imply 3_toes, but it's very likely that an image tagged with avali would also be applicable for having the 3_toes tag. In this system, there would be a section for suggested tags which would be populated based on the already entered tags, so if you enter avali it will suggest 3_toes (and possibly other things like avian). Bonus idea: Clicking the suggestion pastes it into the tag list.
Why would it be useful?
The reason I chose the above example is because 3_toes is not a tag that most people would think of to add. If there were a system to suggest possible tags based on already entered tags, there would be significantly less of a chance of people forgetting to include relevant tags.
What part(s) of the site page(s) are affected?
Uploading, and possibly editing.
Updated