I have a model that I am using texture paint on and I have it posed with an armature. I turned on Texture Paint and have been painting along and realized that some things are not lining up, so I backtracked to document this for others. Here you can see the initial problem with a multiresolution model being painted while in pose and the way the paint doesn't seem to respect the placement regardless of the use of symmetry in paint.
After trial and error I discovered that by turning off visibility in the armature modifier, the symmetry goes back to working. This taught me that the painting symmetry is based on the global coordinates and original position, not the pose it happens to be in. If using Texture Paint with symmetry, toggle the visibility of the armature modifier off for the session unless the misalignment is intentional.