When the user "Mrs. Kitten" adds or remove "Mrs. Kitten" as Subscriber,
usually these messages were generated:

Mrs. Kitten added a subscriber: Mrs. Kitten.
Mrs. Kitten removed a subscriber: Mrs. Kitten.

This was a bit like the Spiderman meme self-pointing Spiderman.

After this change, these beautiful messages are generated instead:

Mrs. Kitten subscribed.
Mrs. Kitten unsubscribed.

Before	After

Closes T15347

• subscribe on something
• unsubscribe from something
• all other cases remain as-is