The bug is difficult to explain. I have the french canadian keyboard (cf). Somes accentued letters, like é, are made by one stroke. Others, like è, are made of two strokes : ` followed by e. The bug affect theses letters. If I open a new mail or a awnser windows, all is ok. I can type à, è and all other letters. But if I open a menu with the mouse, Message by example, and drag the mouse in the next menu, Édition in my case, without selcting anything, in nay menu (just looking successively in two menu) I am no longer able to type the two strokes letters. If I type ` followed by e, I obtain no reaction at all.
This bug has only been reported for versions before 4.14, which have been unsupported for at least two years now. Can anyone tell if this bug still present? If noone confirms this bug for a Framework-based version of kmail2 (version 5.0 or later, as part of KDE Applications 15.12 or later), it gets closed in about three months.
Just as announced in my last comment, I close this bug. If you encounter it again in a recent version (at least 5.0 aka 15.08), please open a new one unless it already exists. Thank you for all your input.