Some bugs are really tricky. So, it's better to have as much information as possible. It makes probability to fix it higher and time to fix it shorter.
Here are some pieces of information which can really help:
1. Go to Thunderbird's Help->Troubleshooting information and attach it to bug report.
2. Make some screenshots and attach them to bug report.
3. Go to MNP options. Set Debug option. Reproduce the bug. Go to TB profile folder and attach the messagenoteplus.log file to bug report.
Even if you collect only step 1 it is still very good.
I'm not interested in your confidential information, but it may accidentally appear in the aforementioned pieces. Please take care to remove it before sending me the report.