Well, I've executed the comparison script with today's HEAD against 3 months ago HEAD and I've got these strings deleted since then:
< blog.php:addotags
< blog.php:addptags
< blog.php:otags
< blog.php:ptags
< countries.php:CS
< countries.php:FX
< countries.php:KO
< countries.php:TP
< countries.php:WA
< countries.php:ZR
< grades.php:aggregationcoefextrahelp
< grades.php:aggregationcoefweighthelp
< grades.php:configbulkcheckboxes
< grades.php:configquickfeedback
< grades.php:errornocategorizedid
< grades.php:overallavg
< moodle.php:nostatstodisplay
< userkey.php:keyiprestrictionhelp
< userkey.php:keyvaliduntilhelp
About these strings... we should test each one to see if they are used in old stable branches:
1) If they are used in stable branches... (say 3 latest branches 1.7, 1.8 and 1.9?) then we must reintroduce them ASAP.
2) If they aren't used, they they only have been in HEAD so, it's safe to keep them deleted, IMO.
Then, two tasks:
A) I think that this task of searching for uses... could be easily automated, to provide the detection script with that useful info.
B The other task would be to detect string files that have changed "a lot" to see if the change is good enough or no. This could be automated too if somebody knows a good algorithm to measure diferences between strings (sure it exists).
In any case... perhaps it would be a goo idea to:
- Move this script to, say, cvs.moodle.org (we need a local checkout of all the branches + head) in the host running the detection script.
- Create some list in lists.moodle.org allowing people to get subscribed to it (Could be 2-3 lists, one with daily changes and another with monthly changes).
- Make the script to send results to that list.
How does it sound?
Ciao 
VIP ( = Very Important People) watchers added for further comments about possible strategies.