Hi André,
There are currently a few places where this _does_ happen:
1) the cosmetic changes fallback. This one is a little difficult to fix -- maybe it should fall back to a hardcoded English string in case i18n is not available?
2) the touch method. The method should probably require summary to be passed as part of the method signature. The corresponding script scripts/touch.py / scripts/newitem.py can then do the i18n lookup.
... in principle, we could also just use a hardcoded summary and not bother translating. After all, touch is supposed to not modify the text and therefore the edit summary _shouldn't be visible_...
Indeed the other approach would be to bundle a subset of i18n data with the framework (these are all in scripts/i18n/pywikibot). However the loading setup is a little bit complex due to the data being json files that could be in a (zipped) Python package...
Cheers,
Merlijn