<span class="Wt-tv-c2 Wt-tv-c rh " title="My ToolTip" id="t_o89i32h">n/a</span>
and when JS is disabled:
<button class="Wt-wrap Wt-tv-c2 Wt-tv-c rh " name="signal=s15d" type="submit"> <span style="margin: 0px -3px -2px -3px;" title="My ToolTip" id="t_o89i3fr">n/a</span> </button>
I suppose, the wrapper covers the and its tool tip is not "reachable" any more. Perhaps, the tool tip have to be transferred to the wrapper when JS is missing.
I'm using wt-3.3.0.