If you wish to discuss Sigil, feel free to do so on the Sigil Forum at MobileRead. This is the official support forum for Sigil and should be used for any questions about user issues. For a list of all changes made to Sigil, you can view the Sigil Changelog or even track updates as they happen.
Also, there is a User Guide and Plugin Developer Guide available in the docs directory. These may not always be up to date but should provide some level of help too. I highly recommend looking at those depending on what you kind of help you need.
Support emails sent directly to Sigil developers will 99.9% of the time go unanswered and will simply be deleted. This is not a business and one on one support is not something that developers can offer or even sustain due to volume. Developers are volunteers and have lives outside of Sigil. This is not a paid product with 8-5 support hours but a community project. Developers often do not have time to reply to support email due to other obligations or because they would rather spend the few hours a week they have (if they even have any time at all) working on Sigil rather than spending that time replying to email. Please use the support forum if you are in need of assistance.