You do not provide enough information to answer your question fully.
In general, you should open a new bug report if you are not quite sure that your bug is the same as the reported (same behaviour, same software/hardware, same log messages, ....).
If you are not sure, you can add a note to your new bug report with a reference to the existing bug report that you think is related. The package maintainers can easily merge reports if needed (splitting reports is much more difficult).
If a bug occurs in several programs, there could be an underlying bug. But especially with hardware/driver-related bugs, there can be a lot of different reasons leading to similar behaviour (like not working suspend or brightness control).
Appending a message to an existing bug report makes only sense if you can add some new relevant information or if want to offer your help (often you can do this already without special knowledge). "Me too"-only-messages should be avoided. This is not the case for bugs tagged unreproducible, here the information that someone else can reproduce them is valuable.
In general, package maintainer are thankful for each bug report or additional information to an existing bug. But flooding them with very similar reports or reports with bad quality should be avoided.
