I go through my konsole history. And when there were some cyrillic letters in commands, it starts garbling the text. Reproducible: Sometimes
Please, check the URL out (a youtube video), I have attached to the bug.
using the up/down keys displaying the shell's history, the cyrillic letters are not displayed correctly
Can you try a newer version? If you still have this issue, can you paste the text you're using. I tried some of the words in konsole/tests/UTF-8-demo.txt and it appears to work here.
Looks like either a bash bug, or non-printable characters in PS1 that are not enclosed between \[ and \]. The original reporter should try under other terminal emulators (e.g. xterm, gnome-terminal), I suspect the bug will be the same there.
Reopen if you can still reproduce the issue with a current konsole version.