This is currently handled with a helper function (src/util/getMonthHeader.ts).

Month is retrieved from mw.language.months.genitive[date.getUTCMonth()]. This should be where the unexpected casing is coming from.

mw.language.months docs - seems like .names rather than .genitive should be used here. If you run mw.language.months.names[0] in your browser console on ruwiki does that give you the expected casing for January?

However layout should be done with i18n anyway, e.g. $1 $2 for en where $1 is month and $2 is year. Something to keep in mind for rewrite

Although there is a point that section title layout is not strictly language-based but by local wiki convention - hence it could be in local config instead of i18n.

Perhaps there should be a separate title for each type of warning.

"vandalism": {
	"name": "Vandalism",
	"category": "common",
	"template": "uw-vandalism",
	"type": "tiered",
	"levels": [
		1,
		2,
		3,
		4,
		5
		],
	"summary": {
		"1": "Destructive editing",
		"2": "Destructive editing"
	}
	"title":"Warning: xg Y"
},