Finally, Khaled added support for display of UTF-8 text as Unicode to mIRC 6.17. Now I think its 6.2, which I tested. Works ok I guess.
The display of UTF-8 can be enabled by default for all windows in the Options/IRC/Messages dialog, or individually for any window you like via the Fonts dialog. Use the /font command to open the fonts dialog.I guess you need to have Dhivehi as a language installed on your windows to have it fully working.