QT for some reason messes with XCompose causing broken input (Qt 5 only - Qt 4 did not break anything). In Qt 5.2 and 5.3 this was causing an invalid conversion in chat messages containing these resulting in the bad bytes being stripped. In Qt 5.9 it is still broken, but you at least get a string with something in it. This checks for non-zero converted strings for room creation and chat lines.
/*
** $Id: lfunc.h,v 2.4.1.1 2007/12/27 13:02:25 roberto Exp $
** Auxiliary functions to manipulate prototypes and closures
** See Copyright Notice in lua.h
*/
#ifndef lfunc_h
#define lfunc_h
#include "lobject.h"
#define sizeCclosure(n) (cast(int, sizeof(CClosure)) + \
cast(int, sizeof(TValue)*((n)-1)))
#define sizeLclosure(n) (cast(int, sizeof(LClosure)) + \
cast(int, sizeof(TValue *)*((n)-1)))
LUAI_FUNC Proto *luaF_newproto (lua_State *L);
LUAI_FUNC Closure *luaF_newCclosure (lua_State *L, int nelems, Table *e);
LUAI_FUNC Closure *luaF_newLclosure (lua_State *L, int nelems, Table *e);
LUAI_FUNC UpVal *luaF_newupval (lua_State *L);
LUAI_FUNC UpVal *luaF_findupval (lua_State *L, StkId level);
LUAI_FUNC void luaF_close (lua_State *L, StkId level);
LUAI_FUNC void luaF_freeproto (lua_State *L, Proto *f);
LUAI_FUNC void luaF_freeclosure (lua_State *L, Closure *c);
LUAI_FUNC void luaF_freeupval (lua_State *L, UpVal *uv);
LUAI_FUNC const char *luaF_getlocalname (const Proto *func, int local_number,
int pc);
#endif