JIRA regular links have a direction attribute: inward or outward. Understanding links directions is critical to work with the Tree View.
In Jira, when an issue (source) is linked to other (target) this link gets the outward direction.
I.e: a Block link type is created between two issues:
source (Blocks) → target
Automatically, Jira creates the reverse link (inward direction):
target (Is blocked by) ← source
Both links are created and stored in the database by Jira.
Lets see practical example:
Let's create a new link of type Blocks between the TALH-8 (source) and the TALH-12 (target) issues:
And from the reverse perspective (by clicking on the TALH-12 issue):
As you can see from images, Links Hierarchy displays the link direction in the tree view. Link directions are shown as arrows pointing from the source to the target always.
Moussing over the issue you will see also a tooltip that shows type of link:
So from direct view (Issue TALH-8 blocks issue TALH-12) you can see outward arrow (image above) , AND
from the reverse view (Issue TALH-12 is blocked by issue TALH-8) you will see inward arrow:
You may find that this rule (Source-Target) doesn't work for Issue splits. In Jira you can see this: (Source issue TALH-10, split to target issues TALH-49, TALH-50) BUT in hierarchy tree we can see inward arrows.
This is because your Jira administrator has reversed the link direction in the app settings. Contact your administrator to find out why it is made. for the reasons for the change.
OR read here about reversed links and scopes:
Reversed Links