Blinded creatures can't make opportunity attacks, so he wouldn't even need to Disengage.

Quote from Jety_Lefr

Nothing in the description of the blinded condition prevents creatures from making opportunity attacks.

 Blinded condition: "A blinded creature can't see"

Opportunity attacks: "You can make an opportunity attack when a hostile creature that you can see moves out of your reach." (my emphasis)

My interpretation of this spell interacting with darkness is that continual flame does not create magical light but a magical flame. So while the flame will not be dispelled by darkness the light it produces will regardless of level. My reason for this decision is because this spell says the fire emulates a torch rather than giving a specific radius of magical light like other light spells do.  In terms of balance I also think its unreasonable for the cost of a third level spell slot to give immunity to second level spell indefinitely. Often for less as continual flame lights are often a common feature of dungeons and probably the most common magic item in existence. 

as a DM i like to follow the rule of cool for spells like this so if someone wanted to cast this on their hand or tail i would say yes but they can't cast it on an unwilling creature which would keep it from being used as a tracking device

it would be good (rule of cool) if spells like this had the Ritual tag.

I'm not sure how D&D decides what spells get Ritual tag. But spells that are 'permanent' or 'prepare and forget' or especially 'useful outside of combat/adventuring' benefit from being rituals, for story purposes, without disrupting anything that I can see. 'Any' noble with a few hundred gold pieces extra, and maybe a court wizard on retainer, can get continually flamed candelabras in their castle. But the court wizard is probably lighting them as a ritual, if just for story purposes.

Or am I missing some disruption that a ritualized casting of continual flame, etc. brings?

https://twitter.com/frozensolid78/status/756543215923331072?s=20

lmao with a tiefling you can make a humanoid charmander, and I love that thought.

All im getting is if this was cast at 3rd or higher it wouldn't be dispelled by darkness. 

It doesnt mean that the darkness wouldnt act as a shroud and cover the spell. 

It just means once ghe darkness is gone or the object moved it will continue to shine again. 

This spell says nothing about fighting,moving,dispelling or removing magical darkness. 

It does however say it acts as a normal torch. 

Would the light generated from the flame be enough for plants to use photosynthesis,  thinking of a way of generating oxygen in a closed location like a bag of holding 

Quote from DiceFarmer >>

I had a dwarf fighter who got the party cleric to cast continual flame on his helm.  He thought it made him look badass.  

...I think he was right.

Bro made himself an unusual

First off, RAW, any spell cast with a higher spell slot is a spell of that level. If you cast Continual Flame with a 9th level slot, it is a 9th level spell.

Secondly, Darkness dispels magical light of the same level or lower. Edit: The spell as written would only effect magical light 2nd level or lower. There is no text that says upcasting the spell increases what level spells it can dispel.

Thirdly, Continual Flame is a magical light with the radius and brightness of a torch, but it is not a torch.

Fourth, Continual Flame produces no heat. You cannot ignite anything without heat.

Therefore, casting Continual Flame at a higher level than the level at which Darkness was cast at would protect Continual Flame from being dispelled. Only a Darkness spell using a 9th level slot can dispel a 9th level Continual Flame. The resulting effect when taking a 3rd level Continual Flame into a 2nd level Darkness would be that it would illuminate the Darkness area as a torch would light an unlit room. Neither spell would be dispelled. The light would only temporarily displace the darkness while within the Darkness spell's radius.

because its essentially permanent, until dispelled. I imagine also because historically it was 2nd level.

Quote from Legerdemain >>

Also, as a counter against Darkness when cast from a 3rd level slot, I would argue that the spell gains nothing from being up-cast, because it doesn't state that it does in the description.
Otherwise it would have given details for 3rd level and higher, with details regarding how much larger and brighter and inextinguishable it is compared to the size and brightness of a torch. Casting it at higher levels doesn't turn it into a brighter or different type of light. It doesn't change at all. It's still a 2nd level magical light, you just expended a higher slot to make it happen.

So if the brightness/size/intensity are no different than that of the 2nd level version, I would argue that since Darkness can dispel its 2nd level form, it would be able to dispel its higher level forms, because there is no change. You would just be willingly throwing away a higher level spell slot. (hopefully only because you ran out of lower level slots)

 no. 

When a spellcaster casts a spell using a slot that is of a higher level than the spell, the spell assumes the higher level for that casting. For instance, if Umara casts magic missile using one of her 2nd-level slots, that magic missile is 2nd level.

Effectively, the spell expands to fill the slot it is put into.

Some spells, such as magic missile and cure wounds, have more powerful effects when cast at a higher level, as detailed in a spell's description.

basic rules, chapter ten

😂 I read all the useful things everyone is using this spell for. Ready for mine?

I nat 20 on playing bagpipes to a crocodile. So I got the nickname “bagpipes”. Gets better, my rogue elf just paid to get the pipes platinum plated. Gotta look good jamming out to bagpipes Metallica. Told another player I want it to shoot flames out of the pipes and I swear I’m not making homemade rocket launchers(could shove a vial in a pipe and makeshift a “dart gun”

Nope the plan is to cast this spell on my modified bagpipes (I think I should get a performance bonus of +2 for flair but oh well), and if I hit nat 20, I go so hard on the pipes you see 15 ft flames shooting out the pipes. Now imagine that going off on a 10ft room :) scary for the party who had fireball trauma.

Interestingly there is no size limitation on this spell, meaning, if the object you choose for the spell is the ground...

Quote from TheTrueChickenKing >>

Interestingly there is no size limitation on this spell, meaning, if the object you choose for the spell is the ground...

 Well it says it is "a flame" (like a torch) not an inferno. So I would imagine you would have a single flame on whatever sized object you put it on. Not a bonfire of several flames on a larger object. At least that is how I read it.

How would a huge fire only have the light source of a single torch?