It seems that as an observer in project, I can enter a new issue, but I cannot comment on it after that. Sometimes I find some extra info, or I make small mistake (just before moment I have entered two defects instead of patches) and I would like to put it there for developers to read - but it seems that after creating issue for first time, I cannot append to it. Same goes for attaching new files - only when first creating it I have possibility to attach files.
While it would be good to allow comments from any observer, it is certainly a must to allow reporter of given issue to add more data to it.