Occasionally on Launchpad, developers ask people to move some discussion of workarounds elsewhere. I don't think this happens a lot, but sometimes such discussion can get in the way of actually investigating and fixing a bug.
I have seen this happen several times. Each time was at a time when I was more involved in bug hunting and less involved in Ask Ubuntu, so when that happened, I never had the thought to propose a "move" to Ask Ubuntu.
In situations where that happens, I wouldn't hesitate to post a question here about workarounds. Of course, Ask Ubuntu is not a discussion forum, but in a situation where workarounds couldn't be presented clearly on Launchpad due to developers' preferences, I think Ask Ubuntu is an appropriate place to ask a "practical, answerable question" about one here.
This is an exception rather than a rule. (AbrahamVanHelpsing articulates another good exception, I think. And there might be others.)
I am not saying "Are there any workarounds for the bug where X happens when you do A" is generally a good, on-topic question for our site.
When posting a question about a workaround after being told not to ask about it in the Launchpad bug page, a link to the developer's bug comment should be included in the question. Because new user restrictions include a restriction on how many links must be posted, this link can and should be added by any editor if not already present.
We might decide--contrary to the perspective presented above--that even this is not something we wish to allow, and that even those questions shouldn't be welcome here. In that case, I think we should then explicitly include hyperlinks to both Launchpad Answers and Ubuntu Forums, in the automatic "off topic" close banner (or maybe even consider a different close reason for questions that relate to bugs, if the Stack Exchange network will provide that to us).