Ukrainian forces are apparently hitting targets in Crimea and within the boundaries of Russia itself. Should we welcome this unreservedly, or worry about escalation?
For now, the former. Putin may view Crimea as part of Russia proper, but nobody else does, so anything within it is a legitimate target. Attacks within Russia are also appropriate if NATO weapons are not used and the targets are purely military in nature. Hitting civilians would be an extremely bad idea, as it would tempt Putin to escalate, and would most likely further mobilize the Russian population in favor of the war.
Personally, I would love to see the Ukrainians destroy Putin’s pet bridge to Crimea. The symbolic impacts of the event would be overwhelming.