I just realized that all the quote boxes are duplicated like the example below on my posts to the
3D (Stereo Photography) topic:
I am almost sure that each post was correct (with just the second quote box) the day I posted and that the duplication took place in a later date.
I have other posts with quote boxes in other topics and they are correct.
Have somebody experienced a similar problem?
Did somebody know why this happened?
I will wait for a while before editing those posts to let you follow the link to them if you like.
I hope to find an answer here mainly to discard a personal error that may cause that weird behavior of the quote tag.