With the new changes in 20w12a you can now look at yourself through iron bars in third person mode due to their transparency. However this does not appear to apply to fences, which seems a bit off, so fences should probably be added to the list of solid transparent blocks that do not block vision.
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slicedlime
This is a feature request.
muzikbike
Here is a list of blocks that you can look through but 3rd person camera can not pass through. And where it might be a bug that the camera does not pass through.
Ladder, fence gates, fences, leaves, (normal) ice, frosted ice, iron door, oak door, jungle door, acacia door, all types of trap doors except dark oak, birch and spruce.