Created attachment 97542 [details] Montage of screenshots illustrating the problem When in block-selection mode with the cursor spanning multiple lines, normal editing changes each line identically. Picking a completion option, however, completes only the first line. After the completion the first part of the completed word is selected on all lines, so that continuing to enter text produces gibberish. The screenshot is probably clearer than my explanation.
I have this issue too on different platforms ((K)ubuntu, Arch and Tumbleweed) and versions (up to the most recent ones). It occurs in Kate, KWrite and KDevelop. I am however not sure wether the bug belongs to frameworks-ktexteditor or to the "part" Component of Kate, which seems to be used in the applications mentioned above.
https://phabricator.kde.org/D18793
*** Bug 408564 has been marked as a duplicate of this bug. ***