All merging does is it retags any questions which had the synonymous tag before the synonym was created. This is just to ensure consistency and make it easier for people to search.
It does and it doesn't. Merging makes the old tag unavailable. Yes, it means when you search you only see one tag, but it still will find the main tag.
On Ask Ubuntu, 12.04lts ...
The problem with this is unwanted tag fragmentation. The reason why umbrella tags are a good thing (especially as we are talking about very few questions here) are described in this answer:
E.g. some of these questions are not specific to climbing, but mountaineering in general. The link to the specific ...
I personally feel that they should not be merged. As Liam already explained the main purpose of tags. These are the keywords that can help us get more visitors and hence potential users.
There are plenty of examples of such tags at the Great Outdoors.
For example, flashlight and torch.
What we (in India) call a battery-powered portable hand-held lamp: a '...