This is closely related to, but distinct from (at present) T324134: Communication: connecting Thanks to a specific edit .

As discussed there, despite thanks from Special:Thanks being tied to revisions, the only way a user can see the ones they've received in full detail is as entries in Special:Notifications, which also can't be filtered by type (see T162930, but originally raised as far back as 2013 in T49093). Special:Log/thanks doesn't show the details of what a user has been thanked for, even in the case of thanks given to the current user (see T51087, also from 2013). As a result, thanks are very obscure once time has passed.

I propose that in addition to the communication improvements proposed at the above task, when logged in and viewing a revision for which they have been thanked, a user is informed of it.

Potential wording for old revision notice at ?title=...&oldid=... (note: "you" added for improved distinction from logged out view):

⚠️ This is an old revision of this page, as edited by you, Username (talk | contribs) at 12:00, 01 January 2024 (Edit summary). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.
(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)
🌟 Username thanked you for this edit at 12:30, 01 January 2024.

And at ?title=...&oldid=prev&diff=...:

Revision as of 12:00, 01 January 2024 (edit) (undo)
You, Username (talk | contribs)
Edit summary
[← Previous edit / Next edit →]
🌟 Username thanked you for this edit at 12:30, 01 January 2024.

In the case of multiple users sending thanks for the same revision, something like:

You were thanked for this edit by:
🌟 Username 1 at 12:30, 01 January 2024
🌟 Username 2 at 13:30, 01 January 2024.

I don't know how common multiple thanks are, but perhaps past a certain number the list should collapse.

You were thanked for this edit by 5 people. [Show]

Not everyone may wish to see this information while looking at page history, so I would also suggest that a feature opt-out for it be added to Special:Preferences.