Thank you for quick response, Rosen.
Actually, user voice portal already contains request to support server-side validation and it is one of the top-voted, so I'm not the only person experiencing this problem.
I see your point, but don't you agree that it is not possible to easily replace a MVC view using standard HTML controls (and obviously validating them on server-side and client side), with Kendo UI client-side controls using Kendo MVC extensions or any other tool, provided by Telerik? It needs a lot of custom development which is repetitive across pages, projects and all your clients.
It would be fine if you just replace HTML and jquery-like controls, leaving existing MVC mechanisms work consistently. But after using Kendo controls the very basic concepts, such as server-side validation, are completely broken.
And not only Telerik team decided not to provide a standard support for such functionality, you even don't make recommendations how it can be done. Support tickets doesn't help a lot either. This creates a gap which is hard to bypass when deciding to use Kendo.
Yesterday I ended up with implementing my own extension method KendoValidationMessageFor() and replacing all MVC ValidationMessageFor() calls with it. I'm not sure whether it's correct approach or no, but I'm sure I've reivented the wheel. I haven't decided yet what to do with grids, validation within Kendo templates, validation of MVVM-bound views and some other problems I foresee.
All those problems didn't exist in native MVC and appeared just in Kendo framework (well, in all similar client-side frameworks to be honest). But Telerik decide to make every developer invent his own solution to common problems instead of tackling them as part of your framework.
PS: I'm sure it would be super-helpful for developers like me (and maybe for telerik team as well to understand our problems) if somebody at Telerik really tries to use their framework for real-world application with at least single complex view (e.g. grid, edit form of which is a complex MVVM-bound view, containing few dozen fields, grouped into tabstrip panes, some 'fields' are grids or listviews itself, datetime fields which display server-timezone time for any client; grid should be groupable (date-only), sortable (date+time) and filterable by this datetime field; it goes without saying everything should support server- and client-side validation, handle errors and edit operation must be transactional). Even it it won't be official example, it will show direction for custom-development of solutions to common problems.