The documentation at: http://docs.topicmapslab.de/majortom/, 3.2. MaJorToM API Feature String, for http://tmapi.org/features/automerge, reads:

"... If the feature is disabled and an application tries to create unique constructs, an error will occurre"

Literally that is saying if this feature is disabled, an application cannot create a unique topic. That can't be correct.

Admittedly the TMAPI language is almost as bad:

"If an implementation does not support this feature, then whenever the implementation detects that two Topics should be merged, it MUST raise an org.tmapi.core.TopicsMustMergeException."

But also noting that only merge by topicName requires the exception.

Solution:

Keep first sentence of the description, replace second sentence with:

"... If the feature is disabled and an application creates two or more topics that should merge using topicName, a org.tmapi.core.TopicsMustMergeException will be raised."

Admittedly it looks like an error in TMAPI but if you are going to follow it, that should do the trick.

thanks for the hint, we replace the description by the description of TMAPI