One big issue with conlangs is that usually, only very few people are knowledgable of their structure, and even fewer know a lot of vocabulary. As such, when being presented with an example sentence in a conlang, the average reader on this site sees exactly gibberish. There are two questions here:
1. Is this a problem?
Given a question on Toki Pona or Lojban, the person who is asking a question is likely at least somewhat familiar with the language and may not require extended explanations or direct translations of features unrelated to the question at hand. For example, in this question here, as of me writing this question, the accepted answer simply features two example sentences in Toki Pona, which the OP presumably understood (or they wouldn’t have accepted the answer). To me as someone who is not familiar with the language’s grammar however, it is unintelligible. I would have been interested in seing the answer stated in a way that I can learn something as well, however. Whether this is a) necessary and b) even desired is in the air.
It can however become an indesputable problem if someone requires help with a feature of their own constructed language. To showcase the context, they will likely require to give some form of examples, and people capable of answering will need to be able to parse those examples, preferrably without much trouble.
Another thing that has to be considered is that examples will not always be about the grammatical structure. Sometimes the focus may be on phonology, in which case the meanings of individual words might be interesting, but not relevant.
The question then is, in what cases do we consider bare example sentences problematic?
2. In cases where we consider it to be a problem, what can we do about it?
Probably the easier question to answer: How do we want people to present example sentences? Do we require glosses, explanations? Do we require a romanization if the language is not written in the latin script? If a question is about phonology, do we require a transcription in a phonetic alphabet, and if yes, does it necessarily have to be IPA or would alternative systems such as Americanist notation be acceptable as well?