There are two areas where doing a positive act might result in negative consequences. The first it publicly thanking people for services performed for the Shul. The second is publicly wishing people Mazal Tov.
When publicly thanking people from the podium or in the newsletter, there is a risk that you will leave someone out and thereby offend them. This can happen at a Shul dinner, where thank yous for general services may be issued, and after specific events. Many people feel that thank yous are so important that they should be issued, even at the risk of leaving someone out. A way to minimize the danger of offending, is by checking your list of thank yous with one or two people, thereby reducing the risk of leaving someone out.
One small caveat is that some people don’t want to be publicly thanked either because they like to keep their chesed private, or because they feel that they did not make a significant enough of a contribution to warrant a public thank you. Some people make a distinction between publicly announced thank yous and those written in the newsletter, as the sting of being left out is more pronounced when it is in print.
There are many lifecycle events that invoke a Mazal Tov, such as a bris, bar/bat mitzvah, engagement, marriage and birth. Mazal Tovs are strong builders of connection, at both the time they are announced and after Shul, when members come over to the Baal Simcha to wish Mazal Tov.
If there is a kiddush in the shul commemorating the event, then public thank yous are certainly in order. In regards to other events, one possible policy is to only announce events that are submitted to the president or some other officer. The downside of such a policy is that people involved in Simchos are usually busy and may forget to submit their Mazal Tov. The upside of such a policy is that there will be less cause for offense, since the lack of an announcement was the result of a lack of notification.
The other possible policy is to encourage submission of Simchos, but announce those that are known even if they are not submitted. The downside of such a policy is that people might be offended if their Simcha is missed, since other non-submitted Simchos where announced. The upside of such a policy is that more Simchos will be announced, resulting in more good will and connection.
I personally feel that Mazal Tovs and their connection generation is so important that they should be announced whenever they are known. Events that are missed can be announced the next week when they are discovered. If such a policy is adopted, members of the Shul should be encouraged to submit Simchos of which they are aware. A caveat here is that some people may not wish a particular Simcha to be announced, specifically when there is a party involved, like a Bat/Bar Mitzvah, and they don’t want to offend people who were not invited.
Life is complicated and setting policy on Thank Yous and Mazal Tovs should be thought through and discussed.