This is clearly a bug.
A work-around is to post-process the output to fix the fence lines:
ClearAll[repairFences]
repairFences = Replace[#, Line[x_] /; Length[Dimensions@x] == 3 :>
(Line[Thread[{#[[;; 2, 2, 1]], #[[1, 1, 2]]}]] & /@ Partition[x, 2]), All] &;
repairFences @
ListLogPlot[Table[{i, Around[1 + Sin[i], 0.1 + 0.1 Cos[i]]}, {i, 0, 10, 1.0}],
PlotRange -> {All, {0.01, 10}},
IntervalMarkers -> "Fences",
IntervalMarkersStyle -> <|"FenceWidth" -> .3|>
]
An alternative work-around is to remove IntervalMarkersStyle -> <|"FenceWidth" -> .3|>
and post-process to modify the fence lines to desired length:
llp2 = ListLogPlot[Table[{i, Around[1 + Sin[i], 0.1 + 0.1 Cos[i]]}, {i, 0, 10, 1.0}],
PlotRange -> {All, {0.01, 10}}, IntervalMarkers -> "Fences" ]
Make fences 20 printer's points long:
llp2 /. Offset[{a_, _}, b_] :> Offset[{10 Sign[a] , 0}, b]
Make fences .3 user units long:
llp2 /. Offset[{a_, _}, {b_, c_}] :> {b + .15 Sign[a], c}