Could not search mention names with special/multibyte characters

Summary

There are no results when searching for mention names with special characters.

Environment

• Web client
• Mac client
• Windows client

Steps to Reproduce

Search for the user's mention name with special/multibyte characters (example: @Tå @田中)

Expected Results

You you will be able to search for the user's mention name.

Actual Results

Search does not yield any results with any special characters in it.

Workaround

Search for the user's actual name instead.