When the sortable option is disabled, the title in the header is not wrapped in span element with 'k-column-title' class.
Rendering with sortable enabled:
The filtering icon and title have enough space:
Rendering with sortable disabled:
filtering icon overlaps the title in case of long text:
The rendering should be identical. The header title should be wrapped in a span element with 'k-column-title' class
Workaround for fixing the overlapping issue:
<style>
.k-grid-header .k-filterable{
padding-right: calc(1.42857143em + 14px);
}
</style>