During some lock debugging on a dual-core Linux system I noticed that threads are blocked acquiring `cs_vNodes` and `cs_main` for long periods when the system is under moderate load from unrelated processes -- the unlucky lock acquirer is waiting for single-digit seconds once every 10 minutes or so (not coinciding with new blocks) up to around a 30 second wait every few hours. It looks like `ThreadMessageHandler` is taking locks and then due to being set to `THREAD_PRIORITY_BELOW_NORMAL`, it's being descheduled (even in trivial lock-holding regions like `GetHeight`) and holding up for arbitrarily long periods other threads that use these core locks.

So I'm wondering, what are the benefits of running the message handler at low priority?

{
    int ret = 0; 
    static bool fStartedNewLine = true;
    string strTimestamped = LogTimestampStr(str, &fStartedNewLine);
    if (fPrintToConsole)
    {
        
        ret = fwrite(strTimestamped.data(), 1, strTimestamped.size(), stdout);
        fflush(stdout);
    }
    else if (fPrintToDebugLog)
    {
        boost::call_once(&DebugPrintInit, debugPrintInitFlag);
        boost::mutex::scoped_lock scoped_lock(*mutexDebugLog);
        
        if (fileout == NULL) {
            assert(vMsgsBeforeOpenLog);
            ret = strTimestamped.length();
            vMsgsBeforeOpenLog->push_back(strTimestamped);